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(PHP 4, PHP 5)
func_get_arg — Liefert ein bestimmtes Funktionsargument
Liefert das mit arg_num angegebene Argument aus der Liste der Argumente einer benutzerdefinierten Funktion.
Diese Funktion kann zusammen mit func_get_args() und func_num_args() genutzt werden um benutzerdefinierte Funktionen mit einer variablen Anzahl von Argumenten zu implementieren.
Der Offset des Arguments. Funktionsargumente werden mit 0 beginnend gezählt.
Liefert das gewünschte Argument oder FALSE bei Fehlern.
| Version | Beschreibung |
|---|---|
| 5.3.0 | Diese Funktion kann nun auch in Parameterlisten genutzt werden. |
Die Funktion generiert eine Warnung wenn sie außerhalb einer benutzerdefinierten Funktion aufgerufen wird oder wenn arg_num größer ist als die Anzahl der tatsächlich übergebenen Argumente.
Beispiel #1 func_get_arg() Beispiel
<?php
function foo()
{
$numargs = func_num_args();
echo "Anzahl der Funktionsargumente: $numargs<br />\n";
if ($numargs >= 2) {
echo "Das zweite Argument ist: " . func_get_arg(1) . "<br />\n";
}
}
foo (1, 2, 3);
?>
Hinweis:
Da diese Funktion bei der Ermittlung der Parameterdetails von dem aktuellen Ausführungskontext abhängt, kann sie in PHP-Versionen vor 5.3.0 selbst nicht als Funktionsparameter genutzt werden. Wenn Sie ihre Ergebnisse tatsächlich weitergeben müssen, so müssen Sie diese zunächst einer Variablen zuweisen und dann diese Variable übergeben
Hinweis: Diese Funktion liefert eine Kopie des übergebenen Arguments. Sie hat nur Zugriff auf tatsächlich übergebene Argumente, Vorgabewerte von Parametern sind für sie nicht sichtbar.
This functions seems so powerful... just when i saw it i thought about writing a fast average of n numbers function so here it is, it is very simple... example usage included.
<?php
//Calculate the average of the numbers given
function avg(){
$sum = 0;
for($i = 0; $i < func_num_args(); $i++){
$sum += func_get_arg($i);
}
$avg = $sum / func_num_args();
return $avg;
}
echo sprintf("%.2f",avg(2,1,2,1,3,4,5,1,3,6));
?>
Bishop: Your ternary example is flawed:
<?php
// using ternary operators
function pick($a,$b) { return (isset($a) ? $a : $b); }
$a = (pick($b,$c) ? pick($c,$d) : null);
?>
If $b is not null, it will evaluate pick($c, $d) and return $c if that is not null. If $b and $c are both null, it will not evaluate pick($c, $d) and will return null regardless of the value of $d. I'm not sure how you'd save this.
Another option would be to use an array:
<?PHP
function pick($array)
{
foreach ($array as $element)
{
if ($element != null)
{
return($element)
}
}
return(null);
}
$a = pick(array($b, $c, $d, $e))
?>
I don't know that there's any real difference between this and the variable-argument form, but some people might prefer it, so it's worth noting.
I was just thinking about a way to create a singleton where you only need to run the instance() function only one time with an argument. And I came up with this solution: (maybe it's useful for other users)
<?php
class Singleton {
private $arg = "";
private function __construct($arg) {
$this->arg = $arg;
}
public static function instance() {
static $_instance = null;
if(func_num_args() == 0 && $_instance == null) {
$_instance = new Singleton(func_get_arg(0));
}
}
}
// first time
$singleton = Singleton::instance("foobar");
// later in your code (in other class and/or function)
$singleton = Singleton::instance();
?>
Regarding a "deferment" operator for dvogel at ssc dot wisc dot edu, pick your poison:
<?php
// using ternary operators
function pick($a,$b) { return (isset($a) ? $a : $b); }
$a = (pick($b,$c) ? pick($c,$d) : null);
?>
<?php
// using varargs function
function pick($a) {
$argc = func_num_args();
for ($i = 0; $i < $argc; $i++) {
$arg = func_get_arg($i);
if (! is_null($arg)) {
return $arg;
}
}
return null;
}
$a = pick($b, $c, $d);
?>
func_get_arg() does not appear to be allowed to be used as a function argument itself within class constructors in PHP 5.0.2 (wonk-ay!!!):
<?php
class ABC
{
function __construct()
{
foreach (func_get_args() as $name => $value)
{
echo <<<EOT
<br/>
$name : $value <br/>
<br/>
EOT;
}
}
}
class DEF extends ABC
{
function __construct()
{
parent::__construct(func_get_arg(0),
func_get_arg(1),
func_get_arg(2));
}
}
$def = new DEF(123123, "asdfasdf", "blahblahblah");
?>
The above script generates:
Fatal error: func_get_arg(): Can't be used as a function parameter in c:\Inetpub\wwwroot\phpwasrc\chapter10\xxx.php on line 23
There are, however, no problems when passing these as parameters to regular functions.
I've always wants a deferment or cascade operator so that I could use this expression:
$a = $b ## $c ## $d;
and everything to the right of the assignment operator would evaluate to the left-most value that is not null. It is essentially a collapsed version of this:
<?php
if ($b) {
$a=$b;
} else {
if($c) {
$a=$c;
} else {
if ($d) {
$a = $d;
} else {
$a = null;
}
}
}
?>
In leiu of this, I'm trying to make a function that takes a variable number of arguments and returns the first that is not null. I wan't to use this on some large-ish arrays, so I'd like to pass these by reference. However, call-time reference passing is disabled (and should be, imo) in newer versions of PHP. I'd like suggestions on how to pass both references and values to this function.
The only solution I can think of is setting variables to the reference of the array first. e.g.
$a = array( ... );
$b = 0;
$c = &a;
first_not_null($a, $b);
Does anyone know a better solution?
func_get_arg is useful, if you know the exact order of the arguments, or if the order doesn't matter. i use this function (or func_get_args) for example to create own sprintf wrappers.
if you want to pass a variable number of arguments to a function it's in my opinion better, to submit it as a key/value array e.g.:
<?php
functioncall(array("param1" => "...",...));
?>
and 'extract' the array inside the function. you don't need to do tricks like type-checking for parameter-recognition, in this case.
I actually think that there is need for such "do absolutely everything" functions. I use them mostly as tools for rapid prototyping.
And there is a method with which you may be able to pass several strings to a function: ereg();
Another use for such functions is to create little code snippets for other people out there. They won't have to edit the function any longer if they do not use a parameter. They just don't name it when calling the function.
This results in allrounder functions that are very robust in their use.Normally you just have a little code snippet (e.g. ip-blocking snippets). Through this type of programming you have whole functions.
very clever unless you need to specify at least two parameters of the same type - which is which? Obviously, you may decide on some defaults, but then the whole thing gets ugly. What if you need a string ONLY if a boolean was also supplied? The type-checking becomes the main focus of your function, shit. For the sake of clean code you should specify a clean interface to your functions, and decide on what and where is passed as an argument. Yes, you can always code a do_absolutely_everything() function, but is there any sense?
A pretty cool thing for user defined functions is only to submit the needed parameters. If you call a function that has three optional parameters you have to define the two first ones (even if they should stay like the defined standard in the function) before your are able to tell the function what the third important parameter is. Instead you might as well just find out by the pattern or the type of the submitted parameter which variable it should be assigned to.
like this:
<?php
function whatever()
{
for($i=0;$i<func_num_args();$i++)
{
if(is_bool(func_get_arg($i))) $log_ip=func_get_arg($i);
if(is_int(func_get_arg($i))) $limit=func_get_arg($i);
if(is_string(func_get_arg($i))) $name=func_get_arg($i);
}
}
?>
Now you can call the function with any parameter you want.
e.g.:
<?php whatever(3600); ?>
in that case $limit would be defined with 3600.
It doesn't matter if you do this:
<?php whatever(3600,false); ?>
or this:
<?php whatever(3600,"blaaah"); ?>
or this:
<?php whatever("blaaah",true,3600); ?>
You may also use ereg(). Through that you're able to use more than one parameter as a string.
hmm probably ereg() is the best solution...
never mind.
just check it out ;-)
func_get_arg() returns a *copy* of the argument, to my knowledge there is no way to retrieve references to a variable number of arguments.
I have a module system in my game at http://lotgd.net where I'd like to be able to pass a variable number of arguments to functions in a module, and pass them by reference if the module asks for it by reference, but you can't accept optional parameters as references, nor can you retrieve the reference on a variable number of arguments. Looks like my modules will have to do with out the ability to accept parameters to their functions by reference.
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