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Überladung bietet in PHP Möglichkeiten, um dynamisch Eigenschaften und Methoden zu "erzeugen". Diese dynamisch erzeugten Entitäten werden unter Zuhilfenahme von magischen Methoden verarbeitet, die man in einer Klasse zu verschiedenen Aktivitäten definieren kann.
Die Überladungsmethoden werden aufgerufen, wenn mit Eigenschaften oder Methoden interagiert wird, die entweder nicht deklariert wurden oder im aktuellen Geltungsbereich nicht sichtbar sind. Im Rest dieses Abschnitts werden die Begriffe "unzugreifbare Eigenschaft" und "unzugreifbare Methode" verwendet, um auf die Kombination von Deklaration und Sichtbarkeit zu verweisen.
Alle Überladungsmethoden müssen als public definiert sein.
Hinweis:
Keiner der Parameter dieser magischen Methoden kann als Referenz übergeben werden.
Hinweis:
Die Interpretation von "Überladung" weicht von den meisten objektorientierten Programmiersprachen ab. Traditionell bezeichnet Überladung die Möglichkeit mehrere Methoden mit gleichem Namen aber unterschiedlichen Anzahlen und Typen von Parametern zu definieren.
| Version | Beschreibung |
|---|---|
| 5.3.0 | __callStatic() hinzugefügt. Eine Warnung wurde hinzugefügt, um die Sichtbakeit public und nicht statische Deklaration zu erzwingen. |
| 5.1.0 | __isset() und __unset() hinzugefügt. |
__set() wird aufgerufen, wenn Daten in unzugreifbare Eigenschaften geschrieben werden sollen.
__get() wird verwendet, um Daten aus unzugreifbaren Eigenschaften zu lesen.
__isset() wird aufgerufen, indem isset() oder empty() auf unzugreifbare Eigenschaften angewendet wird.
__unset() wird aufgerufen, wenn unset() für unzugreifbaren Eigenschaften aufgerufen wird.
Der Parameter $name beinhaltet den Namen der Eigenschaft, mit der interagiert wird. Der Parameter $value der Funktion __set() spezifiziert den Wert den die Eigenschaft $name annehmen soll.
Überladung von Eigenschaften funktioniert nur im Kontext von Objekten. Diese magischen Methoden werden nicht aus einem statischen Kontext aufgerufen. Diese Methoden sollten daher nicht als static deklariert werden. Seit PHP 5.3.0 wird eine Warnung ausgegeben, wemm eine dieser magischen Überladungsmethoden als static deklariert ist.
Hinweis:
Der Rückgabewert von __set() wird, aufgrund der Behandlung des Zuweisungsoperators in PHP, ignoriert. Aus ähnlichen Gründen wird __get() nicht aufgerufen, wenn man Zuweisungen in etwa wie folgt verkettet:
$a = $obj->b = 8;
Beispiel #1 Überladung von Eigenschaften mit den Methoden __get(), __set(), __isset() und __unset()
<?php
class EigenschaftTest {
/** Speicherplatz für überladene Daten. */
private $data = array();
/** Überladung wird nicht bei deklarierten Eigenschaften benutzt. */
public $declared = 1;
/** Überladung wird nur von außerhalb der Klasse angewendet. */
private $hidden = 2;
public function __set($name, $value) {
echo "Setze '$name' auf '$value'\n";
$this->data[$name] = $value;
}
public function __get($name) {
echo "Lese '$name'\n";
if (array_key_exists($name, $this->data)) {
return $this->data[$name];
}
$trace = debug_backtrace();
trigger_error(
'Undefinierte Eigenschaft für __get(): ' . $name .
' in ' . $trace[0]['file'] .
' Zeile ' . $trace[0]['line'],
E_USER_NOTICE);
return null;
}
/** Seit PHP 5.1.0 */
public function __isset($name) {
echo "Ist '$name' gesetzt?\n";
return isset($this->data[$name]);
}
/** Seit PHP 5.1.0 */
public function __unset($name) {
echo "Lösche '$name'\n";
unset($this->data[$name]);
}
/** Keine magische Methode, nur beispielhaft hier. */
public function getHidden() {
return $this->hidden;
}
}
echo "<pre>\n";
$obj = new EigenschaftTest;
$obj->a = 1;
echo $obj->a . "\n\n";
var_dump(isset($obj->a));
unset($obj->a);
var_dump(isset($obj->a));
echo "\n";
echo $obj->declared . "\n\n";
echo "Wir experimentieren nun mit der private-Eigenschaft 'hidden':\n";
echo "Private ist innerhalb der Klasse sichtbar, also wird __get() nicht benutzt...\n";
echo $obj->getHidden() . "\n";
echo "Private nicht sichtbar von außerhalb der Klasse, also wird __get() benutzt...\n";
echo $obj->hidden . "\n";
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
Setze 'a' auf '1' Lese 'a' 1 Ist 'a' gesetzt? bool(true) Lösche 'a' Ist 'a' gesetzt? bool(false) 1 Wir experimentieren nun mit der private-Eigenschaft 'hidden': Private ist innerhalb der Klasse sichtbar, also wird __get() nicht benutzt... 2 Private nicht sichtbar von außerhalb der Klasse, also wird __get() benutzt... Lese 'hidden' Notice: Undefinierte Eigenschaft für __get(): hidden in <file> Zeile 70 in <file> on line 29
__call() wird aufgerufen, wenn eine unzugreifbare Methode in einem Objekt aufgerufen wird.
__callStatic() wird aufgerufen, wenn eine unzugreifbare Methode in einem statischen Kontext aufgerufen wird.
Der Parameter $name ist der Name der aufgerufenen Methode. Der Parameter $arguments beinhaltet ein Array mit den Parametern, die der Methode $name übergeben wurden.
Beispiel #2 Überladung von Methoden mit den methoden __call() und __callStatic()
<?php
class MethodenTest {
public function __call($name, $arguments) {
// Achtung: Der Wert von $name beachtet die Groß-/Kleinschreibung
echo "Rufe die Objektmethode '$name' "
. implode(', ', $arguments). "\n";
}
/** Seit PHP 5.3.0 */
public static function __callStatic($name, $arguments) {
// Achtung: Der Wert von $name beachtet die Groß-/Kleinschreibung
echo "Rufe die statische Methode '$name' "
. implode(', ', $arguments). "\n";
}
}
$obj = new MethodenTest;
$obj->runTest('eines Objektes auf');
MethodTest::runTest('aus statischem Kontext auf'); // Seit PHP 5.3.0
?>
Das oben gezeigte Beispiel erzeugt folgende Ausgabe:
Rufe die Objektmethode 'runTest' eines Objektes auf Rufe die statische Methode 'runTest' aus statischem Kontext auf
Using anon functions, you can allow your class methods to be declared after your class is already set. Though you cannot use a class property as a function in any way (including for properties that are objects with their own __invoke() method) without triggering a fatal error, there is a workaround using an array property to store all these anon functions...
<?php
class Test {
// generic class allowing dynamic addition of methods
public $anon_list = array(); // list of all custom added methods
function __call($fnc, $args) {return call_user_func_array($this->anon_list[$fnc], $args);}
function __set($name, $val) {$this->anon_list[$name] = $val;}
}
// Example adding a new custom method
$test = new Test;
$test->do_something = function ($var1, $var2) {echo "custom called with $var1 and $var2\n";};
$test->do_something('asdf', 'test');
?>
Unfortunately, without access to $this within the anon functions, it's not really useful. You can "use ($test)" in your anon function, but that just makes it more complicated.
Note that __isset is not called on chained checks.
If isset( $x->a->b ) is executed where $x is a class with __isset() declared, __isset() is not called.
<?php
class demo
{
var $id ;
function __construct( $id = 'who knows' )
{
$this->id = $id ;
}
function __get( $prop )
{
echo "\n", __FILE__, ':', __LINE__, ' ', __METHOD__, '(', $prop, ') instance ', $this->id ;
return new demo( 'autocreated' ) ; // return a class anyway for the demo
}
function __isset( $prop )
{
echo "\n", __FILE__, ':', __LINE__, ' ', __METHOD__, '(', $prop, ') instance ', $this->id ;
return FALSE ;
}
}
$x = new demo( 'demo' ) ;
echo "\n", 'Calls __isset() on demo as expected when executing isset( $x->a )' ;
$ret = isset( $x->a ) ;
echo "\n", 'Calls __get() on demo without call to __isset() when executing isset( $x->a->b )' ;
$ret = isset( $x->a->b ) ;
?>
Outputs
Calls __isset() on demo as expected when executing isset( $x->a )
C:\htdocs\test.php:31 demo::__isset(a) instance demo
Calls __get() on demo without call to __isset() when executing isset( $x->a->b )
C:\htdocs\test.php:26 demo::__get(a) instance demo
C:\htdocs\test.php:31 demo::__isset(b) instance autocreated
If you want to make it work more naturally for arrays $obj->variable[] etc you'll need to return __get by reference.
<?php
class Variables
{
public function __construct()
{
if(session_id() === "")
{
session_start();
}
}
public function __set($name,$value)
{
$_SESSION["Variables"][$name] = $value;
}
public function &__get($name)
{
return $_SESSION["Variables"][$name];
}
public function __isset($name)
{
return isset($_SESSION["Variables"][$name]);
}
}
?>
Dynamic getting-setting using __call and __callStatic
<?php
class A {
private $fields;
public function __call($func, $args) {
if (empty($args)) {
return $this->fields[$args[0]];
} else {
$this->$fields[$func] = $args[0];
}
}
?>
Or statically:
<?php
class foo {
static $vals;
public static function __callStatic($func, $args) {
if (!empty($args)) {
self::$vals[$func] = $args[0];
} else {
return self::$vals[$func];
}
}
}
?>
Which would allow you to say:
<?php
Foo::username('john');
print Foo::username(); // prints 'john'
?>
I've written a brief, generic function for __get() and __set() that works well implementing accessor and mutator functions.
This allows the programmer to use implicit accessor and mutator methods when working with attribute data.
<?php
class MyClass
{
private $degrees
public function __get($name)
{
$fn_name = 'get_' . $name;
if (method_exists($this, $fn_name))
{
return $this->$fn_name();
}
else
{
return null;
}
}
public function __set($name, $value)
{
$fn_name = 'set_' . $name;
if (method_exists($this, $fn_name))
{
$this->$fn_name($value);
}
}
private function get_degrees()
{
return $this->degrees;
}
private function set_degrees($value)
{
$this->degrees = $value % 360;
if ($degrees < 0) $this->degrees += 360;
}
}
?>
I've written a brief, generic function for __get() and __set() that works well implementing accessor and mutator functions.
This allows the programmer to use implicit accessor and mutator methods when working with attribute data.
<?php
class MyClass
{
private $degrees
public function __get($name)
{
$fn_name = 'get_' . $name;
if (method_exists($this, $fn_name))
{
return $this->$fn_name();
}
else
{
return null;
}
}
public function __set($name, $value)
{
$fn_name = 'set_' . $name;
if (method_exists($this, $fn_name))
{
$this->$fn_name($value);
}
}
private function get_degrees()
{
return $this->degrees;
}
private function set_degrees($value)
{
$this->degrees = $value % 360;
if ($degrees < 0) $this->degrees += 360;
}
}
?>
TRICKY CHALLENGE: is there a way to check if $object->variable exists without automatically triggering the functionality of __get in case the variable doesn't exist?
TRADITIONAL WAY:
<?php
$object = new someClass(); // imagine someClass uses the Magic Method "__get"
if($object->variable){
// do something
} else {
// "__get" has inevitably been triggered :-(
}
?>
Ok, above we have the conventional way to check if a variable exists inside the object, the problem is that sometimes we DON'T WANT TO TRIGGER __GET in case the statement returns false!
ALTERNATIVE WAY:
<?php
if(array_key_exists( 'variable', get_object_vars($object) ) ){
// do something
} else {
// "__get" has no idea what is going on, i think it is still asleep :-)
}
?>
you can even turn this into a function or something
Combining two things noted previously:
1 - Unsetting an object member removes it from the object completely, subsequent uses of that member will be handled by magic methods.
2 - PHP will not recursively call one magic method from within itself (at least for the same $name).
This means that if an object member has been unset(), it IS possible to re-declare that object member (as public) by creating it within your object's __set() method, like this:
<?php
class Foo
{
function __set($name, $value)
{
// Add a new (public) member to this object.
// This works because __set() will not recursively call itself.
$this->$name= $value;
}
}
$foo = new Foo();
// $foo has zero members at this point
var_dump($foo);
// __set() will be called here
$foo->bar = 'something'; // Calls __set()
// $foo now contains one member
var_dump($foo);
// Won't call __set() because 'bar' is now declared
$foo->bar = 'other thing';
?>
Also be mindful that if you want to break a reference involving an object member without triggering magic functionality, DO NOT unset() the object member directly. Instead use =& to bind the object member to any convenient null variable.
It says in the documentation that assignment chaining does not work with the __set() function like this:
<?php
$a = $foo->b = 3;
?>
If you still want to make it work, I suppose you can just turn the variables around:
<?php
$foo->b = $a = 3;
?>
By using __call, we can use php as using jQuery:
<?php
//SoWork PHP Framework
define('this', mt_rand());
$o='so_work';
class cls_so_work
{function __call($fun, $pars)
{foreach ($pars as &$v)
{if ($v===this)
{$v=$this->val;
break;
}
}
$tmp=eval('return defined("'.$fun.'")?constant("'.$fun.'"):"'.$fun.'";');
$this->val=call_user_func_array($tmp, $pars);
return $this;
}
function cls_so_work($obj)
{$this->val=isset($obj)?$obj:null;
}
}
function so_work($obj)
{if (isset($obj))
{return new cls_so_work($obj);
}
else
{if (!isset($GLOABALS['so_work']))
{$GLOABALS['so_work']=new cls_so_work();
}
else
{$GLOABALS['so_work']->val=null;
}
return $GLOABALS['so_work'];
}
}
define('echo', 'my_echo');
function my_echo($obj)
{echo $obj;
return $obj;
}
$o('abcd')->substr(this, 2, 2)->strlen(this)->echo(this);
$o()->substr('abcd', 1, 3)->strlen(this)->echo(this);
?>
I needed to know from where a member variable was set from to determine visibility.
<?php
class foo {
private $data;
public function __set($name, $value) {
$trace = debug_backtrace();
if(!isset($trace[1]) || $trace[1]['object'] != $trace[0]['object']) {
die("Trying to set protected member '$name' from public scope.");
}
$data[$name] = $value;
}
}
?>
It is possible to accomplish method polymorphism via PHP's __call method:
<?php
class Example{
public function __call($name, $arguments){
switch($name){
case 'foo':
switch(count($arguments)){
case 2:
echo 'You called "foo" with two arguments.<br>' . PHP_EOL;
break;
case 3:
echo 'You called "foo" with three arguments.<br>' . PHP_EOL;
break;
default:
echo 'Error: Invalid number of arguments to "foo."<br>' . PHP_EOL;
break;
}
break;
default:
echo "Error: Call to undefined function \"$name.\"<br>" . PHP_EOL;
}
}
}
$test = new Example;
$test->foo('bar', 'baz');
$test->foo('bar', 'baz', 'fez', 'fap');
$test->bar();
?>
Just another note about using __get() & __set() on array properties with PHP v5.2.0.
Took me quite a while to find out why I couldn't write an array property that was created via __set(). Now a few notes earlier someone described a working solution using the ArrayObject-class. This does work, but has a big downside, you cannot expect other programmers to know that they will be getting an instance of ArrayObject instead of a native array, and trying to do an implode() on an ArrayObject will just not work. So, here is my solution to the problem:
<?php
class A {
private $properties = array();
public function __set($key, $value) {
if (is_array($value)) {
$this->$key = $value;
} else {
$this->properties[$key] = $value;
}
}
public function __get($key) {
if (array_key_exists($key, $this->properties)) {
return $this->properties[$key];
}
return null;
}
}
?>
The idea behind this is, that you can register new properties at any time from within a class without getting a warning or some of that kind. Now, if you try to set a property from outside the class, the __set() method will be called and decides whether to place the new property in the properties array or declare it as a new "native" property. When trying to get that property, the __get() method will only be called if the property is not "native", which won't be the case for an array.
HTH
Here's a handy little routine to suggest properties you're trying to set that don't exist. For example:
Attempted to __get() non-existant property/variable 'operator_id' in class 'User'.
checking for operator and suggesting the following:
* id_operator
* operator_name
* operator_code
enjoy.
<?php
/**
* Suggests alternative properties should a __get() or __set() fail
*
* @param string $property
* @return string
* @author Daevid Vincent [daevid@daevid.com]
* @date 05/12/09
* @see __get(), __set(), __call()
*/
public function suggest_alternative($property)
{
$parts = explode('_',$property);
foreach($parts as $i => $p) if ($p == '_' || $p == 'id') unset($parts[$i]);
echo 'checking for <b>'.implode(', ',$parts)."</b> and suggesting the following:<br/>\n";
echo "<ul>";
foreach($this as $key => $value)
foreach($parts as $p)
if (stripos($key, $p) !== false) print '<li>'.$key."</li>\n";
echo "</ul>";
}
just put it in your __get() or __set() like so:
public function __get($property)
{
echo "<p><font color='#ff0000'>Attempted to __get() non-existant property/variable '".$property."' in class '".$this->get_class_name()."'.</font><p>\n";
$this->suggest_alternative($property);
exit;
}
?>
If you got a parent class agregating(not inheriting) a number of child classes in an array, you can use the following to allow calling methods of the parent object on agregated child objects:
<?php
class child {
public $holder = null;
public function __call($name, $arguments) {
if($this->holder instanceof parentClass && method_exists($this->holder, $name)) {
return call_user_func_array(array($this->holder, $name), $arguments);
}
else {
trigger_error();
}
}
}
class parentClass {
private $children = array();
function __construct() {
$this->children[0] = new child();
$this->children[0]->holder = $this;
}
function getChild($number) {
if(!isset($this->children[$number])) {
return false;
}
return $this->children[$number];
}
function test() {
return 'it works';
}
}
$parent = new parentClass();
$firstChild = $parent->getChild(0);
echo $firstChild->test(); //should output 'it works'
?>
This is a great way to give different permissions to parent classes.
<?php
class A{
private $b;
function foo(){
$this->b = new B;
echo $this->b->protvar;
}
}
class B extends A{
protected $protvar="protected var";
public function __get($nm) {
echo "Default $nm value";
}
}
$a = new A;
$b = new B;
$a->foo(); // prints "protected var"
echo $b->protvar; // prints "Default protvar value"
?>
This way, you can help parent classes to have more power with protected members.
Be extra careful when using __call(): if you typo a function call somewhere it won't trigger an undefined function error, but get passed to __call() instead, possibly causing all sorts of bizarre side effects.
In versions before 5.3 without __callStatic, static calls to nonexistent functions also fall through to __call!
This caused me hours of confusion, hopefully this comment will save someone else from the same.
<?php
/***********************************************
*And here follows a child class which implements a menu based in the 'nodoMenu' class (previous note).
*
*[]s
*
*erick2711 at gmail dot com
************************************************/
class menu extends nodoMenu{
private $cssc = array();
public function __toString(){ //Just to show, replace with something better.
$stringMenu = "<pre>\n";$stringMenu .= $this->strPrint();$stringMenu .= "</pre>\n";
return $stringMenu;
}
public function __construct($cssn = null){
parent::__construct();
if (isset($cssn) && is_array($cssn)){$this->cssc = $cssn;}
$this->buildMenu();
}
public function buildMenu(){
$this->add('server',
'Server',
'server.php');
$this->server->add('personalD',
'Personal Data',
'server/personal.php');
$this->server->add('personalI',
'Personal Interviews',
'server/personalI.php');
$this->server->personalI->add('detailsByIer',
'Detalis by Interviewer',
'server/personalI.php?tab=detailsByIer');
//(...)
return $this;
}
}
//Testing
$meuMenu = new menu;
echo $meuMenu;
/***********************************************
*Will output (to the browser):
*
*<pre>
*1 Server<br>
* 1.1 Personal Data<br>
* 1.2 Personal Interviews<br>
* 1.2.1 Details by Interviewer<br>
*</pre>
*
*Which shows:
*
*1 Server
* 1.1 Personal Data
* 1.2 Personal Interviews
* 1.2.1 Details by Interviewer
************************************************/
?>
<?php
/*
Here folows a little improvement of the 'strafvollzugsbeamter at gmx dot de' code, allowing each node to hold both 'parameters' and 'child nodes', and differentiate $s->A->B->C ('FOO') from $s->A (same 'FOO', but shouldn't exist) and from $s-A->B (idem).
This allows the class, using the interesting suggested syntax ($root->dad->child->attribute, in which 'dad's and 'child's names are dynamically generated), to do something actually useful, like implementing a n-tree data structure (a menu, for instance).
It was tested under PHP 5.2.6 / Windows.
I know that must there be something better which already do this (probably in the DOM Model classes, or something like), but it was fun to develop this one, for the sake of studying the "magic" methods.
Its a compressed version of the code (no comments, too short variable names, almost no identation). I had to compress it in order to add the note. If anyone cares about the full version, just email me.
[]s
erick2711 at gmail dot com
*/
class nodoMenu{
protected $p = array();
protected $c = array();
public function __construct($t = '', $uri = '', $css = null, $n = 0, $i=0){
$this->p['t'] = $t;$this->p['uri'] = $uri;$this->p['css'] = $css;$this->p['n'] = $n;$this->p['i'] = $i;$this->p['q'] = 0;return $this;
}
public function add($cn, $ct = '', $cl = '', $css = null){
$nc = new nodoMenu($ct, $cl, $css, $this->p['n'] + 1, $this->p['q']);$this->c[$cn] = $nc;$this->p['q'] += 1;return $this->c[$cn];
}
private function isParameter($pn){
return array_key_exists($pn, $this->p);
}
public function __isset($pn){
if ($this->isParameter($pn)){return(!is_null($this->p[$pn]));}
else{return(array_key_exists($pn, $this->c));}
}
public function remove($cn){
if (array_key_exists($cn, $this->c)){$this->p['q'] -= 1;unset($this->c[$cn]);}
}
public function __unset($pn){
if ($this->isParameter($pn)){$this->p[$pn] = null;}
else{$this->remove($pn);}
}
public function __set($pn, $v){
$r = null;
if ($this->isParameter($pn)){$this->p[$pn] = $v;$r = $v;}
else{if (array_key_exists($pn, $this->c)){$this->c[$pn] = $v;$r = $this->c[$pn];}
else{$r = $this->add($pn);}}
return $r;
}
public function __get($pn){
$v = null;
if ($this->isParameter($pn)){$v = $this->p[$pn];}
else{if (array_key_exists($pn, $this->c)){$v = $this->c[$pn];}
else{$v = $this->add($pn);}}
return $v;
}
public function hasChilds(){
return(isset($this->c[0]));
}
public function child($i){
return $this->c[$i];
}
public function strPrint($bm = ''){ //Just to show, replace with something better.
$m = '';$r = '';$n = $this->p['n'];
if ($n > 0){switch($n){case 0:case 1: $qs = 0; break;case 2: $qs = 2; break;case 3: $qs = 6; break;case 4: $qs = 12; break;case 5: $qs = 20; break;case 6: $qs = 30; break;case 7: $qs = 42; break;case 8: $qs = 56; break;}
$tab = str_repeat(' ', $qs);$r .= $tab;
if ($bm <> ''){$m = $bm.'.';}
$im = $this->p['i'] + 1;$m .= $im;$r .= $m.' ';$r .= $this->p['t']."<br>\n";
}
foreach ($this->c as $child){$r .= $child->strPrint($m);}
return $r;
}
public function __toString(){
return $this->strPrint();
}
}
?>
There's nothing wrong with calling these functions as normal functions:
If you end up in a situation where you need to know the return value of your __set function, just write <?php $a = $obj->__set($var, $val); ?> instead of <?php $a = $obj->$var = $val; ?>.
The following works on my installation (5.2.6 / Windows):
<?php
class G
{
private $_p = array();
public function __isset($k)
{
return isset($this->_p[$k]);
}
public function __get($k)
{
$v = NULL;
if (array_key_exists($k, $this->_p))
{
$v = $this->_p[$k];
}
else
{
$v = $this->{$k} = $this;
}
return $v;
}
public function __set($k, $v)
{
$this->_p[$k] = $v;
return $this;
}
}
$s = new G();
$s->A->B->C = 'FOO';
$s->X->Y->Z = array ('BAR');
if (isset($s->A->B->C))
{
print($s->A->B->C);
}
else
{
print('A->B->C is NOT set');
}
if (isset($s->X->Y->Z))
{
print_r($s->X->Y->Z);
}
else
{
print('X->Y->Z is NOT set');
}
// prints: FOOArray ( [0] => BAR )
?>
... have fun and ...
This is a generic implementation to use getter, setter, issetter and unsetter for your own classes.
<?php
abstract class properties
{
public function __get( $property )
{
if( ! is_callable( array($this,'get_'.(string)$property) ) )
throw new BadPropertyException($this, (string)$property);
return call_user_func( array($this,'get_'.(string)$property) );
}
public function __set( $property, $value )
{
if( ! is_callable( array($this,'set_'.(string)$property) ) )
throw new BadPropertyException($this, (string)$property);
call_user_func( array($this,'set_'.(string)$property), $value );
}
public function __isset( $property )
{
if( ! is_callable( array($this,'isset_'.(string)$property) ) )
throw new BadPropertyException($this, (string)$property);
return call_user_func( array($this,'isset_'.(string)$property) );
}
public function __unset( $property )
{
if( ! is_callable( array($this,'unset_'.(string)$property) ) )
throw new BadPropertyException($this, (string)$property);
call_user_func( array($this,'unset_'.(string)$property) );
}
}
?>
you CAN write into ARRAYS by using __set and __get magic functions.
as has been mentioned before $obj->var['key'] = 'test'; does call the __get method of $obj, and there is no way to find out, if the method has been called for setting purposes.
the solution is quite simple: use __get to return the array by reference. then you can write into it:
<?php
class setter{
private $_arr = array();
public function __set($name, $value){
$this->_arr[$name] = $value;
}
public function &__get($name){
if (isset($this->_arr[$name])){
return $this->_arr[$name];
} else return null;
}
}
?>
PHP4 supports using __call but with a twist that I did not see mentioned anywhere on this page.
In 4, you must make the __call method signature with 3 parameters, the 3rd of which is the return value and must be declared by-reference. Instead of using "return $value;" you would assign the 3rd argument to $value.
Example (both implementations below have the same result when run in the respective PHP versions:
<?php
// Will only work in PHP4
class Foo
{
function __call($method_name, $parameters, &$return_value)
{
$return_value = "Method $method_name was called with " . count($parameters) . " parameters";
}
}
// Will only work in PHP5
class Foo
{
function __call($method_name, $parameters)
{
return "Method $method_name was called with " . count($parameters) . " parameters";
}
}
?>
Several users have mentioned ways to allow setting of array properties via magic methods. In particular, PHP calls the __get() method instead of the __set() method when you try to do: $obj->prop['offset'] = $val.
The suggestions that I've read below all work, except that they do not allow you make properties read-only. After a bit of struggling, I have found a solution. Essentially, if the property is supposed to be a read-only array, create an new ArrayObject() out of it, then clone it and return the clone.
<?php
public function __get($var) {
if(isset($this->read_only_props[$var])) {
$ret = null;
if (is_array($this->read_only_props[$var]))
return clone new ArrayObject($this->read_only_props[$var]);
else if (is_object($this->read_only_props[$var]))
return clone $this->read_only_props[$var];
else
return $this->read_only_props[$var];
}
else if (!isset($this->writeable_props[$var]))
$this->writeable_props[$var] = NULL;
return $this->writeable_props[$var];
}
public function __set($var, $val) {
if (isset($this->read_only_props[$var]))
throw new Exception('tried to set a read only property on the event object');
return $this->writeable_props[$var] = $val;
}
?>
Note that __get() does not explicitly return by reference as many examples have suggested. Also, I have not found a way to detect when __get() is being called for setting purposes, thus my code can not throw an exception when necessary in these cases.
The __get overload method will be called on a declared public member of an object if that member has been unset.
<?php
class c {
public $p ;
public function __get($name) { return "__get of $name" ; }
}
$c = new c ;
echo $c->p, "\n" ; // declared public member value is empty
$c->p = 5 ;
echo $c->p, "\n" ; // declared public member value is 5
unset($c->p) ;
echo $c->p, "\n" ; // after unset, value is "__get of p"
?>
There isn't some way to overload a method when it's called as a reflection method:
<?php
class TestClass {
function __call($method, $args) {
echo "Method {$method} called with args: " . print_r($args, TRUE);
}
}
$class = new ReflectionClass("TestClass");
$method = $class->getMethod("myMehtod");
//Fatal error: Uncaught exception 'ReflectionException' with message 'Method myMethod' does not exist'
?>
Juan.
In response to Anonymous: 09-Jan-2008 10:45.
PHP 5.3 will include the magic method __callStatic to use for static method calls.
see also:
http://bugs.php.net/bug.php?id=26739
If you want to be able to overload a variable from within a class and this is your code:
<?php
class myClass
{
private $data;
public function __set($var, $val)
{
$this->data[$var] = $val;
}
public function __get($var)
{
$this->data[$var] = $val;
}
}
?>
There is a problem if you want to call these variables from within the class, as you you want to access data['data'] then you can't say $this->data as it will return the array $data. Therefore a simple solution is to name the array $_data. So in your __get and __set you will say $this->_data ... rather than $this->data. I.E:
<?php
class myClass
{
private $_data;
public function __set($var, $val)
{
$this->_data[$var] = $val;
}
public function __get($var)
{
$this->_data[$var] = $val;
}
}
?>
Umang
the documentation states a falsehood:
"All overloading methods must be defined as public."
<?php
class test{
#################
#public use methods#
#################
public static function echoData(){
$obj = self::getInstance();
echo $obj->find('data');
return true;
}
######################
#only use a single instance#
######################
private static $instance;
private static function getInstance(){
if(!isset(self::$instance)){
self::$instance = new test;
}
return self::$instance;
}
#################
#private instantiation#
#################
private $data = array('data'=>'i am data');
private function __construct(){}
private function __call($nm,$args){
if(isset($this->data[$args[0]])){
return $this->data[$args[0]];
}
return null;
}
}
test::echoData();
?>
--------------OUTPUT---------------
i am data
-----------------------------------
this test was run using PHP Version 5.2.4
it should be noted that __call will trigger only for method calls on an instantiated object, and cannot be used to 'overload' static methods. for example:
<?php
class TestClass {
function __call($method, $args) {
echo "Method {$method} called with args: " . print_r($args, TRUE);
}
}
// this will succeed
$obj = new TestClass();
$obj->method_doesnt_exist();
// this will not
TestClass::method_doesnt_exist();
?>
It would be useful if the PHP devs would include this in a future release, but in the meantime, just be aware of that pitfall.
The PHP devs aren't going to implement true overloading because: PHP is not strictly typed by any stretch of the imagination (0, "0", null, false, and "" are the same, for example) and unlike Java and C++, you can pass as many values as you want to a function. The extras are ignored unless you fetch them using func_get_arg(int) or func_get_args(), which is often how I "overload" a function/method, and fewer than the declared number of arguments will generate an E_WARNING, which can be suppressed by putting '@' before the function call, but the function will still run as if you had passed null where a value was expected.
<?php
class someClass {
function whatever() {
$args = func_get_args();
// public boolean whatever(boolean arg1) in Java
if (is_bool($args[0])) {
// whatever(true);
return $args[0];
// public int whatever(int arg1, boolean arg2) in Java
} elseif(is_int($args[0]) && is_bool($args[1])) {
// whatever(1, false)
return $args[0];
} else {
// public void whatever() in Java
echo 'Usage: whatever([int], boolean)';
}
}
}
?>
// The Java version:
public class someClass {
public boolean whatever(boolean arg1) {
return arg1;
}
public int whatever(int arg1, boolean arg2) {
return arg1;
}
public void whatever() {
System.out.println("Usage: whatever([int], boolean)");
}
}
While PHP does not support true overloading natively, I have to disagree with those that state this can't be achieved trough __call.
Yes, it's not pretty but it is definately possible to overload a member based on the type of its argument. An example:
<?php
class A {
public function __call ($member, $arguments) {
if(is_object($arguments[0]))
$member = $member . 'Object';
if(is_array($arguments[0]))
$member = $member . 'Array';
$this -> $member($arguments);
}
private function testArray () {
echo "Array.";
}
private function testObject () {
echo "Object.";
}
}
class B {
}
$class = new A;
$class -> test(array()); // echo's 'Array.'
$class -> test(new B); // echo's 'Object.'
?>
Of course, the use of this is questionable (I have never needed it myself, but then again, I only have a very minimalistic C++ & JAVA background). However, using this general principle and optionally building forth on other suggestions a 'form' of overloading is definately possible, provided you have some strict naming conventions in your functions.
It would of course become a LOT easier once PHP'd let you declare the same member several times but with different arguments, since if you combine that with the reflection class 'real' overloading comes into the grasp of a good OO programmer. Lets keep our fingers crossed!
You can't use __set to set arrays, but if you really want to, you can emulate it yourself:
<?php
class test {
public $x = array();
public $y = array();
function __set($var, $value)
{
if ( preg_match('/(.*)\[(.*)\]/', $var, $names) ) {
$this->y[$names[1]][$names[2]] = $value;
}
else {
$this->x[$var] = $value;
}
}
}
$z = new test;
$z->variable = 'abc';
$z->{'somearray[key]'} = 'def';
var_dump($z->x);
var_dump($z->y);
?>
This is a misuse of the term overloading. This article should call this technique "interpreter hooks".
@ zachary dot craig at goebelmediagroup dot com
I do something like that, too. My way might be even more clunky.
<?php
function sum() {
$args = func_get_args();
if (!count($args)) {
echo 'You have to supply something to the function.';
} elseif (count($args) == 1) {
return $args[0];
} elseif (count($args) == 2) {
if (is_numeric($args[0]) && is_numeric($args[1])) {
return $args[0] + $args[1];
} else {
return $args[0] . $args[1];
}
}
}
?>
I like the "__call" method, though. You can "declare" multiple functions that don't pollute the namespace. Although, it might be better looking to use this instead of a series of if...elseif... statemenets.
<?php
class myClass {
function __call($fName, $fArgs) {
switch($fName) {
case 'sum':
if (count ($fArgs) === 1) {
return $fArgs[0];
} else {
$retVal = 0;
foreach( $fArgs as $arg ) {
$retVal += $arg;
}
return $retVal;
}
break;
case 'other_method':
...
default:
die ('<div><b>Fetal Error:</b> unknown method ' . $fName . ' in ' . __CLASS__ . '.</div>');
} // end switch
}
}
?>
Side note: if you don't force lower/upper case, you will have case sensitive method names. E.g. $myclass->sum() !== $myclass->Sum().
@egingell at sisna dot com -
Use of __call makes "overloading" possible also, although somewhat clunky... i.e.
<?php
class overloadExample
{
function __call($fName, $fArgs)
{
if ($fName == 'sum')
{
if (count ($fArgs) === 1)
{
return $fArgs[0];
}
else
{
$retVal = 0;
foreach( $fArgs as $arg )
{
$retVal += $arg;
}
return $retVal;
}
}
}
}
/*
Simple and trivial I realize, but the point is made. Now an object of class overloadExample can take
*/
echo $obj->sum(4); // returns 4
echo $obj->sum(4, 5); // returns 9
?>
"These methods will only be triggered when your object or inherited object doesn't contain the member or method you're trying to access."
is not quite correct:
they get called when the member you trying to access in not visible:
<?php
class test {
public $a;
private $b;
function __set($name, $value) {
echo("__set called to set $name to $value\n");
$this->$name = $value;
}
}
$t = new test;
$t->a = 'a';
$t->b = 'b';
?>
Outputs:
__set called to set b to b
Be aware that set ist not called for public properties
Let us look at the following example:
<?php
class objDriver {
private $value;
public function __construct()
{
$value = 1;
}
public function doSomething($parameterList)
{
//We make actions with the value
}
}
class WantStaticCall {
private static $objectList;
private function __construct()
public static function init()
{
self::$objectList = array();
}
public static function register($alias)
{
self::$objectList[$alias] = new objDriver();
}
public static function __call($method, $arguments)
{
$alias = $arguments[0];
array_shift($arguments);
call_user_method($method, self::$objectList[$alias], $arguments);
}
}
// The deal here is to use following code:
WantStaticCall::register('logger');
WantStaticCall::doSomething('logger', $argumentList);
// and we will make objDriver to call his doSomething function with arguments
// $argumentList. This is not common pattern but very usefull in some cases.
// The problem here is that __call() cannot be static, Is there a way to work it around
?>
Just to clarify something the manual states about method overloading.
"All overloading methods must be defined as public."
As of PHP 5.2.2, this should be considered more of a coding convention rather than a requirement. In PHP 5.2.2, declaring a __get or __set function with a visibility other than public, will be silently ignored by the parser and will not trigger a parse error!
What is more, PHP will completely ignore the visibility modifier either of these functions are declared with and will always treat them as if they were public.
I am not sure if this is a bug or not so to be on the safe side,
stick with always declaring them public.
Small vocabulary note: This is *not* "overloading", this is "overriding".
Overloading: Declaring a function multiple times with a different set of parameters like this:
<?php
function foo($a) {
return $a;
}
function foo($a, $b) {
return $a + $b;
}
echo foo(5); // Prints "5"
echo foo(5, 2); // Prints "7"
?>
Overriding: Replacing the parent class's method(s) with a new method by redeclaring it like this:
<?php
class foo {
function new($args) {
// Do something.
}
}
class bar extends foo {
function new($args) {
// Do something different.
}
}
?>
Just Noting the interesting behavior of __set __get , when modifying objects contained in overloaded properties.
<?php
class foo {
public $propObj;
public function __construct(){
$propObj = new stdClass();
}
public function __get($prop){
echo("I'm Being Got ! \n");
return $this->propObj->$prop;
}
public function __set($prop,$val){
echo("I'm Being Set ! \n");
$this->propObj->$prop = $val;
}
}
$test = new foo();
$test->barProp = new stdClass(); // I should invoke set
$test->barProp->barSubProp = 'As Should I';
$test->barProp->barSubProp = 'As Should I';
$test->barProp = new stdClass(); // As should i
?>
Outputs:
I'm Being Set !
I'm Being Got !
I'm Being Got !
I'm Being Set !
Whats happening, is PHP is acquiring a reference to the object, triggering __get; Then applying the changes to the object via the reference.
Which is the correct behaviour; objects being special creatures, with an aversion to being cloned...
Unfortunately this will never invoke the __set handler, even though it is modifying a property within 'foo', which is slightly annoying if you wanted to keep track of changes to an objects overloaded properties.
I guess Journaled Objects will have to wait till PHP 6 :)
Please note, this example will not work on later PHP versions. You must return from __get() by reference using &__get()
Just to reinforce and elaborate on what DevilDude at darkmaker dot com said way down there on 22-Sep-2004 07:57.
The recursion detection feature can prove especially perilous when using __set. When PHP comes across a statement that would usually call __set but would lead to recursion, rather than firing off a warning or simply not executing the statement it will act as though there is no __set method defined at all. The default behaviour in this instance is to dynamically add the specified property to the object thus breaking the desired functionality of all further calls to __set or __get for that property.
Example:
<?php
class TestClass{
public $values = array();
public function __get($name){
return $this->values[$name];
}
public function __set($name, $value){
$this->values[$name] = $value;
$this->validate($name);
}
public function validate($name){
/*
__get will be called on the following line
but as soon as we attempt to call __set
again PHP will refuse and simply add a
property called $name to $this
*/
$this->$name = trim($this->$name);
}
}
$tc = new TestClass();
$tc->foo = 'bar';
$tc->values['foo'] = 'boing';
echo '$tc->foo == ' . $tc->foo . '<br>';
echo '$tc ' . (property_exists($tc, 'foo') ? 'now has' : 'still does not have') . ' a property called "foo"<br>';
/*
OUPUTS:
$tc->foo == bar
$tc now has a property called "foo"
*/
?>
Observe:
<?php
class Foo {
function __call($m, $a) {
die($m);
}
}
$foo = new Foo;
print $foo->{'wow!'}();
// outputs 'wow!'
?>
This method allows you to call functions with invalid characters.
PHP 5.2.1
Its possible to call magic methods with invalid names using variable method/property names:
<?php
class foo
{
function __get($n)
{
print_r($n);
}
function __call($m, $a)
{
print_r($m);
}
}
$test = new foo;
$varname = 'invalid,variable+name';
$test->$varname;
$test->$varname();
?>
I just don't know if it is a bug or a feature :)
While playing a bit with the __call magic method I found you can not emulate implementing methods of an interface as you might think:
<?php
class Iteratable implements Iterator {
public function __call($funcname) {
if(in_array($funcname, array('current', 'next', /*...*/)) {
//Redirect the call or perform the actual action
}
}
}
?>
Using this code you'll get a "class Iteratable contains abstract methods ..." fatal error message. You'll ALWAYS have to implement those routines by hand.
In reply to james at thunder-removeme-monkey dot net,
Unfortunately it seems that there is no way to have completely transparent array properties with 5.2.x. The code you supplied works until working with built-in functions that perform type-checks:
<?php
// Using the same View class
$view = new View();
$view->bar = array();
$view->bar[] = "value";
if (is_array($view->bar))
print "is array!\n"; // Not printed
// Warning: in_array(): Wrong datatype for second argument in ...
if (in_array("value", $view->bar))
print "found!\n"; // Not printed
// Successful
if (in_array("value", (array)$view->bar))
print "found!\n";
?>
It also seems that 5.1.x is no longer maintained as it's not listed on the downloads page.. Quite frustrating. :/
As a reply to james at thunder-removeme-monkey dot net, I found that there is a much simpler way to restore the behavior of __get() to 5.1.x state; just force __get() to return by reference, like this:
<?php
class View {
/* Somewhere to store our overloaded properties */
private $v = array();
/* Store a new property */
function __set($varName, $varValue) {
$this->v[$varName] = $varValue;
}
/* Retrieve a property */
function & __get($varName) {
if(!isset($this->v[$varName])) {
$this->v[$varName] = NULL;
}
return $this->v[$varName];
}
}
?>
The only problem is that the code generates a notice if null is returned in __get(), because null cannot be returned by reference. If somebody finds a solution, feel free to email me. :)
Cheers
Following up on the comment by "jstubbs at work-at dot co dot jp" and after reading "http://weierophinney.net/matthew/archives/ 131-Overloading-arrays-in-PHP-5.2.0.html", the following methods handle property overloading pretty neatly and return variables in read/write mode.
<?php
class View {
/* Somewhere to store our overloaded properties */
private $v = array();
/* Store a new property */
function __set($varName, $varValue) {
$this->v[$varName] = $varValue;
}
/* Retrieve a property */
function __get($varName) {
if(!isset($this->v[$varName])) {
$this->v[$varName] = NULL;
}
return is_array($this->v[$varName]) ? new ArrayObject($this->v[$varName]) : $this->v[$varName];
}
}
?>
This is an amalgm of previous solutions with the key difference being the use of ArrayObject in the return value. This is more flexible than having to extend the whole class from ArrayObject.
Using the above class, we can do ...
<?php
$obj = new SomeOtherObject();
$view = new View();
$view->list = array();
$view->list[] = "hello";
$view->list[] = "goat";
$view->list[] = $group;
$view->list[] = array("a", "b", "c");
$view->list[3][] = "D";
$view->list[2]->aprop = "howdy";
/*
$view->list now contains:
[0] => "hello"
[1] => "goat"
[2] => SomeOtherObject { aprop => "howdy" }
[3] => array("a", "b", "c", "D")
and
$obj === $view->list[2] // equates to TRUE
*/
?>
example for read only properties in class object. Lets you manage read only properties with var names like $ro_var.
The property must be PRIVATE, otherwise the overload method __get doesn't be called.
<?php
class Session {
private $ro_usrName;
function __construct (){
$this->ro_usrName = "Marcos";
}
function __set($set, $val){
if(property_exists($this,"ro_".$set))
echo "The property '$set' is read only";
else
if(property_exists($this,$set))
$this->{$set}=$val;
else
echo "Property '$set' doesn't exist";
}
function __get{$get}{
if(property_exists($this,"ro_".$get))
return $this->{"ro_".$get};
else
if(property_exists($this,$get))
return $this->{$get};
else
echo "Property '$get' doesn't exist";
}
}
?>
Since many here probably wanted to do «real» overloading without having to think too much, here's a generic __call() function for those cases.
Little example :
<?php
class OverloadedClass {
public function __call($f, $p) {
if (method_exists($this, $f.sizeof($p))) return call_user_func_array(array($this, $f.sizeof($p)), $p);
// function does not exists~
throw new Exception('Tried to call unknown method '.get_class($this).'::'.$f);
}
function Param2($a, $b) {
echo "Param2($a,$b)\n";
}
function Param3($a, $b, $c) {
echo "Param3($a,$b,$c)\n";
}
}
$o = new OverloadedClass();
$o->Param(4,5);
$o->Param(4,5,6);
$o->ParamX(4,5,6,7);
?>
Will output :
Param2(4,5)
Param3(4,5,6)
Fatal error: Uncaught exception 'Exception' with message 'Tried to call unknown method OverloadedClass::ParamX' in overload.php:7
Stack trace:
#0 [internal function]: OverloadedClass->__call('ParamX', Array)
#1 overload.php(22): OverloadedClass->ParamX(4, 5, 6, 7)
#2 {main}
thrown in overload.php on line 7
<?php $myclass->foo['bar'] = 'baz'; ?>
When overriding __get and __set, the above code can work (as expected) but it depends on your __get implementation rather than your __set. In fact, __set is never called with the above code. It appears that PHP (at least as of 5.1) uses a reference to whatever was returned by __get. To be more verbose, the above code is essentially identical to:
<?php
$tmp_array = &$myclass->foo;
$tmp_array['bar'] = 'baz';
unset($tmp_array);
?>
Therefore, the above won't do anything if your __get implementation resembles this:
<?php
function __get($name) {
return array_key_exists($name, $this->values)
? $this->values[$name] : null;
}
?>
You will actually need to set the value in __get and return that, as in the following code:
<?php
function __get($name) {
if (!array_key_exists($name, $this->values))
$this->values[$name] = null;
return $this->values[$name];
}
?>
This is just my contribution. It based off of many diffrent suggestions I've see thought the manual postings.
It should fit into any class and create default get and set methods for all you member variables. Hopfuly its usefull.
<?php
public function __call($name,$params)
{
if( preg_match('/(set|get)(_)?/',$name) )
{
if(substr($name,0,3)=="set")
{
$name = preg_replace('/set(_)?/','',$name);
if(property_exists(__class__,$name))
{
$this->{$name}=array_pop($params);
return true;
}
else
{
//call to class error handler
return false;
}
return true;
}
elseif(substr($name,0,3)=="get")
{
$name = preg_replace('/get(_)?/','',$name);
if(property_exists(__class__,$name) )
{
return $this->{$name};
}
else
{
//call to class error handler
return false;
}
}
else
{
//call to class error handler
return false;
}
}
else
{
die("method $name dose not exist\n");
}
return false;
}
Regarding the post by TJ earlier, about the problems extending DOMElement. Yes, it is true that you can't set extDOMElement::ownerDocument directly; however, you could append the extDOMElement to a DOMDocument in __construct(), which indirectly sets ownerDocument. It should work something like so:
<?php
class extDOMElement extends DOMElement {
public function __construct(DOMDocument $doc) {
$doc->appendChild($this); //extDOMElement::ownerDocument is now equal to the object that $doc points to
}
}
?>
Now, I admit I've never actually needed to do this, but I see no reason why it shouldn't work.
Yet another way of providing support for read-only properties. Any property that has
"pri_" as a prefix will NOT be returned, period, any other property will be returned
and if it was declared to be "protected" or "private" it will be read-only. (scope dependent of course)
<?php
function __get($var){
if (property_exists($this,$var) && (strpos($var,"pri_") !== 0) )
return $this->{$var};
else
//Do something
}
?>
If you're wondering how to create read-only properties for your class, the __get() and __set() functions are what you're looking for. You just have to create the framework and code to implement this functionality.
Here's a quick example I've written. This code doesn't take advantage of the "type" attribute in the properties array, but is there for ideas.
<?php
class Test {
private $p_arrPublicProperties = array(
"id" => array("value" => 4,
"type" => "int",
"readonly" => true),
"datetime" => array("value" => "Tue 02/21/2006 20:49:23",
"type" => "string",
"readonly" => true),
"data" => array("value" => "foo",
"type" => "string",
"readonly" => false)
);
private function __get($strProperty) {
//Get a property:
if (isset($this->p_arrPublicProperties[$strProperty])) {
return $this->p_arrPublicProperties[$strProperty]["value"];
} else {
throw new Exception("Property not defined");
return false;
}
}
private function __set($strProperty, $varValue) {
//Set a property to a value:
if (isset($this->p_arrPublicProperties[$strProperty])) {
//Check if property is read-only:
if ($this->p_arrPublicProperties[$strProperty]["readonly"]) {
throw new Exception("Property is read-only");
return false;
} else {
$this->p_arrPublicProperties[$strProperty]["value"] = $varValue;
return true;
}
} else {
throw new Exception("Property not defined");
return false;
}
}
private function __isset($strProperty) {
//Determine if property is set:
return isset($this->p_arrPublicProperties[$strProperty]);
}
private function __unset($strProperty) {
//Unset (remove) a property:
unset($this->p_arrPublicProperties[$strProperty]);
}
}
$objTest = new Test();
print $objTest->data . "\n";
$objTest->data = "bar"; //Works.
print $objTest->data;
$objTest->id = 5; //Error: Property is read-only.
?>
Please note that PHP5 currently doesn't support __call return-by-reference (see PHP Bug #30959).
Example Code:
<?php
class test {
public function &__call($method, $params) {
// Return a reference to var2
return $GLOBALS['var2'];
}
public function &actual() {
// Return a reference to var1
return $GLOBALS['var1'];
}
}
$obj = new test;
$GLOBALS['var1'] = 0;
$GLOBALS['var2'] = 0;
$ref1 =& $obj->actual();
$GLOBALS['var1']++;
echo "Actual function returns: $ref1 which should be equal to " . $GLOBALS['var1'] . "<br/>\n";
$ref2 =& $obj->overloaded();
$GLOBALS['var2']++;
echo "Overloaded function returns: $ref2 which should be equal to " . $GLOBALS['var2'] . "<br/>\n";
?>
Here's a useful class for logging function calls. It stores a sequence of calls and arguments which can then be applied to objects later. This can be used to script common sequences of operations, or to make "pluggable" operation sequences in header files that can be replayed on objects later.
If it is instantiated with an object to shadow, it behaves as a mediator and executes the calls on this object as they come in, passing back the values from the execution.
This is a very general implementation; it should be changed if error codes or exceptions need to be handled during the Replay process.
<?php
class MethodCallLog {
private $callLog = array();
private $object;
public function __construct($object = null) {
$this->object = $object;
}
public function __call($m, $a) {
$this->callLog[] = array($m, $a);
if ($this->object) return call_user_func_array(array(&$this->object,$m),$a);
return true;
}
public function Replay(&$object) {
foreach ($this->callLog as $c) {
call_user_func_array(array(&$object,$c[0]), $c[1]);
}
}
public function GetEntries() {
$rVal = array();
foreach ($this->callLog as $c) {
$rVal[] = "$c[0](".implode(', ', $c[1]).");";
}
return $rVal;
}
public function Clear() {
$this->callLog = array();
}
}
$log = new MethodCallLog();
$log->Method1();
$log->Method2("Value");
$log->Method1($a, $b, $c);
// Execute these method calls on a set of objects...
foreach ($array as $o) $log->Replay($o);
?>
Problem: $a->b->c(); when b is not instantiated.
Answer: __get()
<?php
class a
{
function __get($v)
{
$this->$v = new $v;
return $this->$v;
}
}
class b
{
function say($word){
echo $word;
}
}
$a = new a();
$a->b->say('hello world');
// echos 'hello world'
?>
Using the getter/setter methods to provide read-only access to object properties breaks the conventional understanding of inheritence.
A super class using __set() to make a property read-only cannot be properly inherited because the visible (read-only) property - with conventional public or protected visibility - cannot be set in the sub-class.
The sub-class cannot overload the super class's __set() method either, and therefore the inheritence is severely compromised.
I discovered this issue while extending DOMDocument and particularly DOMElement.
When extDOMDocument->createElement() creates a new extDOMElement, extDOMElement->__construct() can't set the extDOMElement->ownerDocument property because it's read-only.
DOMElements are totally read-only if they do not have an ownerDocument, and there's no way to set it in this scenario, which makes inheritence pretty pointless.
This allows you to seeminly dynamically overload objects using plugins.
<?php
class standardModule{}
class standardPlugModule extends standardModule
{
static $plugptrs;
public $var;
static function plugAdd($name, $mode, $ptr)
{
standardPlugModule::$plugptrs[$name] = $ptr;
}
function __call($fname, $fargs)
{ print "You called __call($fname)\n";
$func = standardPlugModule::$plugptrs[$fname];
$r = call_user_func_array($func, array_merge(array($this),$fargs));
print "Done: __call($fname)\n";
return $r;
}
function dumpplugptrs() {var_dump(standardPlugModule::$plugptrs); }
}
class a extends standardPlugModule
{ function text() { return "Text"; } }
//Class P contained within a seperate file thats included
class p
{ static function plugin1($mthis, $r)
{ print "You called p::plugin1\n";
print_r($mthis);
print_r($r);
}
} a::plugAdd('callme', 0, array('p','plugin1'));
//Class P contained within a seperate file thats included
class p2
{ static function plugin2($mthis, $r)
{ print "You called p2::plugin2\n";
$mthis->callme($r);
}
} a::plugAdd('callme2', 0, array('p2','plugin2'));
$t = new a();
$testr = array(1,4,9,16);
print $t->text()."\n";
$t->callme2($testr);
//$t->dumpplugptrs();
?>
Will result in:
----------
Text
You called __call(callme2)
You called p2::plugin2
You called __call(callme)
You called p::plugin1
a Object
(
[var] =>
)
Array
(
[0] => 1
[1] => 4
[2] => 9
[3] => 16
)
Done: __call(callme)
Done: __call(callme2)
----------
This also clears up a fact that you can nest __call() functions, you could use this to get around the limits to __get() not being able to be called recursively.
To those who wish for "real" overloading: there's not really any advantage to using __call() for this -- it's easy enough with func_get_args(). For example:
<?php
class Test
{
public function Blah()
{
$args = func_get_args();
switch (count($args))
{
case 1: /* do something */ break;
case 2: /* do something */ break;
}
}
}
?>
By Design (http://bugs.php.net/bug.php?id=33998) you cannot call a getter from a getter or any function triggered by a getter:
<?php
class test
{
protected $_a = 6;
function __get($key) {
if($key == 'stuff') {
return $this->stuff();
} else if($key == 'a') {
return $this->_a;
}
}
function stuff()
{
return array('random' => 'key', 'using_getter' => 10 * $this->a);
}
}
$test = new test();
print 'this should be 60: '.$test->stuff['using_getter'].'<br/>'; // prints "this should be 60: 0"
// [[ Undefined property: test::$a ]] on /var/www/html/test.php logged.
print 'this should be 6: '.$test->a.'<br/>'; // prints "this should be 6: 6"
?>
Please note that PHP5's overloading behaviour is not compatible at all with PHP4's overloading behaviour.
for anyone who's thinking about traversing some variable tree
by using __get() and __set(). i tried to do this and found one
problem: you can handle couple of __get() in a row by returning
an object which can handle consequential __get(), but you can't
handle __get() and __set() that way.
i.e. if you want to:
<?php
print($obj->val1->val2->val3); // three __get() calls
?> - this will work,
but if you want to:
<?php
$obj->val1->val2 = $val; // one __get() and one __set() call
?> - this will fail with message:
"Fatal error: Cannot access undefined property for object with
overloaded property access"
however if you don't mix __get() and __set() in one expression,
it will work:
<?php
$obj->val1 = $val; // only one __set() call
$val2 = $obj->val1->val2; // two __get() calls
$val2->val3 = $val; // one __set() call
?>
as you can see you can split __get() and __set() parts of
expression into two expressions to make it work.
by the way, this seems like a bug to me, will have to report it.
Keep in mind that when your class has a __call() function, it will be used when PHP calls some other magic functions. This can lead to unexpected errors:
<?php
class TestClass {
public $someVar;
public function __call($name, $args) {
// handle the overloaded functions we know...
// [...]
// raise an error if the function is unknown, just like PHP would
trigger_error(sprintf('Call to undefined function: %s::%s().', get_class($this), $name), E_USER_ERROR);
}
}
$obj = new TestClass();
$obj->someVar = 'some value';
echo $obj; //Fatal error: Call to undefined function: TestClass::__tostring().
$serializedObj = serialize($obj); // Fatal error: Call to undefined function: TestClass::__sleep().
$unserializedObj = unserialize($someSerializedTestClassObject); // Fatal error: Call to undefined function: TestClass::__wakeup().
?>
You can't mix offsetSet() of the ArrayAccess interface (http://www.php.net/~helly/php/ext/spl/interfaceArrayAccess.html) and __get() in the same line.
Below, "FileManagerPrefs" is an object of class UserData which implements ArrayAccess. There's a protected array of UserData objects in the User class, which are returned from __get().
<?php
// This produces an error...
Application::getInstance()->user->FileManagerPrefs[ 'base'] = 'uploads/jack';
?>
Creates this error:
Fatal error: Cannot access undefined property for object with overloaded property access in __FILE__ on line __LINE__
However, __get() and offsetGet() play deceptively well together.
<?php
// This works fine!
echo Application::getInstance()->user->FileManager['base'];
?>
I guess it's a dereferencing issue with __get(). In my case, it makes more sense to have a middle step (user->data['FileManager']['base']), but I wanted to tip off the community before I move on.
<?php
## THE PROBLEM: Class with lots of attributes.
## You want to use $o->getVarName() or $o->get_varname() style getters
## Some attributes have custom get functions, but the rest don't
## THE SOLUTION: __call
class Person
{
## this top stuff is just an example. could be anything.
private $name;
private $age;
private $weight;
function __construct($name, $age, $weight)
{
$this->name = $name;
$this->age = $age;
$this->weight = $weight;
}
## PORTABLE: use this __call function in any class
function __call($val, $x)
{
# see if they're calling a getter method - and try to guess the variable requested
if(substr($val, 0, 4) == 'get_')
{
$varname = substr($val, 4);
}
elseif(substr($val, 0, 3) == 'get')
{
$varname = substr($val, 3);
}
else
{
die("method $val does not exist\n");
}
# now see if that variable exists:
foreach($this as $class_var=>$class_var_value)
{
if(strtolower($class_var) == strtolower($varname))
{
return $class_var_value;
}
}
return false;
}
# IMPORTANT: you can keep some things private - or treat
# some vars differently by giving them their own getter method
# See how this function lies about Person's weight.
function getWeight()
{
return intval($this->weight * .8);
}
}
$a = new Person('Miles', 35, 200);
# these all work (case-insensitive):
print $a->get_name() . "\n";
print $a->getName() . "\n";
print $a->get_Name() . "\n";
print $a->getname() . "\n";
print $a->get_age() . "\n";
print $a->getAge() . "\n";
print $a->getage() . "\n";
print $a->get_Age() . "\n";
# defined functions still override the __call
print $a->getWeight() . "\n";
# trying to get something that doesn't exist returns false
print $a->getNothing();
# this still gets error:
print $a->hotdog();
?>
<?php
abstract class BubbleMethod
{
public $objOwner;
function __call($sMethod, $aParams)
{
// Has the Owner been assigned?
if (isset($this->objOwner))
{
return call_user_func_array(array($this->objOwner, $sMethod), $aParams);
}
else
{
echo 'Owner for ' . get_class($this) . ' not assigned.';
}
}
}
class A_WebPageContainer
{
private $sName;
public function __construct($sName)
{
$this->sName = $sName;
}
public function GetWebPageContainerName()
{
return $this->sName;
}
}
class A_WebFrame extends BubbleMethod
{
private $sName;
public function __construct($sName)
{
$this->sName = $sName;
}
public function GetWebFrameName()
{
return $this->sName;
}
}
class A_WebDocument extends BubbleMethod
{
private $sName;
public function __construct($sName)
{
$this->sName = $sName;
}
public function GetWebDocumentName()
{
return $this->sName;
}
}
class A_WebForm extends BubbleMethod
{
private $sName;
public function __construct($sName)
{
$this->sName = $sName;
}
public function GetWebFormName()
{
return $this->sName;
}
}
class A_WebFormElement extends BubbleMethod
{
private $sName;
public function __construct($sName)
{
$this->sName = $sName;
}
public function GetWebFormElementName()
{
return $this->sName;
}
}
$objWPC = new A_WebPageContainer('The outer web page container.');
$objWF1 = new A_WebFrame('Frame 1');
$objWF1->objOwner = $objWPC;
$objWF2 = new A_WebFrame('Frame 2');
$objWF2->objOwner = $objWPC;
$objWD1 = new A_WebDocument('Doc 1');
$objWD1->objOwner = $objWF1;
$objWD2 = new A_WebDocument('Doc 2');
$objWD2->objOwner = $objWF2;
$objWFrm1 = new A_WebForm('Form 1');
$objWFrm1->objOwner = $objWD1;
$objWFrm2 = new A_WebForm('Form 2');
$objWFrm2->objOwner = $objWD2;
$objWE1 = new A_WebFormElement('Element 1');
$objWE1->objOwner = $objWFrm1;
$objWE2 = new A_WebFormElement('Element 2');
$objWE2->objOwner = $objWFrm1;
$objWE3 = new A_WebFormElement('Element 3');
$objWE3->objOwner = $objWFrm2;
$objWE4 = new A_WebFormElement('Element 4');
$objWE4->objOwner = $objWFrm2;
echo "The name of the form that '" . $objWE1->GetWebFormElementName() . "' is in is '" . $objWE1->GetWebFormName() . "'<br />";
echo "The name of the document that '" . $objWE2->GetWebFormElementName() . "' is in is '" . $objWE2->GetWebDocumentName(). "'<br />";
echo "The name of the frame that '" . $objWE3->GetWebFormElementName() . "' is in is '" . $objWE3->GetWebFrameName(). "'<br />";
echo "The name of the page container that '" . $objWE4->GetWebFormElementName() . "' is in is '" .$objWE4->GetWebPageContainerName(). "'<br />";
?>
Results in.
The name of the form that 'Element 1' is in is 'Form 1'
The name of the document that 'Element 2' is in is 'Doc 1'
The name of the frame that 'Element 3' is in is 'Frame 2'
The name of the page container that 'Element 4' is in is 'The outer web page container.'
By using the abstract BubbleMethod class as the starting point for further classes that are contained inside others (i.e. elements on a form are contained in forms, which are contained in documents which are contained in frames which are contained in a super wonder global container), you can find properties of owner without knowing their direct name.
Some work needs to be done on what to do if no method exists though.
A few things I've found about __get()...
First off, if you use $obj->getOne->getAnother, both intended to be resolved by __get, the __get() function only sees the first one at first. You can't access the second one. You can, however, return the pointer to an object that can handle the second one. In short, you can have the same class handle both by returning a new object with the data changed however you see fit.
Secondly, when using arrays like: $obj->getArray["one"], only the array name is passed on to __get. However, when you return the array, PHP treats it just as it should. THat is, you'd have to make an array with the index of "one" in __get in order to see any results. You can also have other indexes in there as well.
Also, for those of you like me, I've already tried to use func_get_args to see if you can get more than just that one.
If you're like me and were hoping you could pass some sort of argument onto __get in order to help gather the correct data, you're out of look. I do recommend using __call though. You could easily rig __call up to react to certain things, like: $account->properties( "type" );, which is my example. I'm using DOM for data storage (for now), and I'm trying to make an interface that'll let me easily switch to something else - MySQL, flat file, anything. This would work great though!
Hope I've been helpful and I hope I didn't restate something already stated.
For anyone who is interested in overloading a class method based on the number of arguments, here is a simplified example of how it can be accomplished:
<?php
function Error($message) { trigger_error($message, E_USER_ERROR); exit(1); }
class Framework
{
// Pseudo function overloading
public function __call($func_name, $argv)
{
$argc = sizeof($argv);
switch ($func_name) {
case 'is_available':
$func_name = ($argc == 2) ? 'is_available_single' : 'is_available_multi';
break;
default: // If no applicable function was found, generate the default PHP error message.
Error('Call to undefined function Framework::'. $func_name .'().');
}
return call_user_func_array(array(&$this, $func_name), $argv);
}
// protected array is_available_multi($mod_name, $mod_addon_0 [, $mod_addon_1 [, ...]])
protected function is_available_multi()
{
if (($argc = func_num_args()) < 2) {
Error('A minimum of two arguments are required for Framework::is_available().');
}
$available_addons = array();
// --snip--
return $available_addons;
}
protected function is_available_single($mod_name, $mod_addon)
{
// --snip--
return true;
}
}
$fw = new Framework;
$test_one = $fw->is_available('A_Module_Name', 'An_Addon');
var_dump($test_one);
// Test one produces a boolean value, supposedly representing whether 'An_Addon' is available and can be used.
$test_two = $fw->is_available('A_Module_Name', 'Addon_0', 'Addon_1', 'Addon_2');
var_dump($test_two);
// Test two produces an array, supposedly listing any of the three 'Addon_N' modules that are available and can be used.
// Here are the actual results of the above:
// bool(true)
// array(0) {
// }
?>
---
By adding additional case statements to Framework::__call(), methods can easily be overloaded as needed. It's also possible to add any other overloading criteria you require inside the switch statement, allowing for more intricate overloading functionality.
Php 5 has a simple recursion system that stops you from using overloading within an overloading function, this means you cannot get an overloaded variable within the __get method, or within any functions/methods called by the _get method, you can however call __get manualy within itself to do the same thing.
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