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(PHP 4, PHP 5)
func_num_args — Liefert die Anzahl der an eine Funktion übergebenen Argumente
Liefert die Anzahl der Argumente die an die aufrufende Funktion übergeben wurden.
Diese Funktion kann zusammen mit func_get_arg() und func_get_args() genutzt werden um Funktionen mit einer variablen Anzahl von Argumenten zu implementieren.
Liefert die Anzahl der Argumente die beim Aufruf an die aufrufenden Funktion übergeben wurden.
| Version | Beschreibung |
|---|---|
| 5.3.0 | Diese Funktion kann nun auch in Parameterlisten genutzt werden. |
Die Funktion generiert eine Warnung wenn sie von außerhalb einer benutzerdefinierten Funktion aufgerufen wird.
Beispiel #1 func_num_args() Beispiel
<?php
function foo()
{
$numargs = func_num_args();
echo "Anzahl der Argumente: $numargs\n";
}
foo(1, 2, 3); // Ergebnis: 'Anzahl der Argumente: 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
This function comes in handy, and I believe is the only solution, when you have an optional parameter that can take any type of data.
For example:
<?php
// $data can be of any type, including null
function my_function($name, $data = null)
{
if ($data !== null)
{
// Do something with $data
// If you call my_function('something'), this WILL NOT be reached
// If you call my_function('something', null), this WILL NOT be reached
}
}
?>
The problem with the above function is that you will never be able to use null as the value for $data. To fix this, use func_num_args() like so:
<?php
// $data can be of any type, including null
function my_function($name, $data = null)
{
if (func_num_args() >= 2)
{
// Do something with $data
// If you call my_function('something'), this WILL NOT be reached
// If you call my_function('something', null), this WILL be reached
}
}
?>
This solution works because func_num_args() reports exactly how many arguments were passed when the function was called. It does not take into account when default argument values are used.
func_num_args(), func_get_args() and func_get_arg() can be very useful to emulate overloading in PHP.
Suppose you have a class to add a user in a system, and that you want to allow 2 ways of doing it. The first way would be passing an array with all the user info in it, and the second way would be passing each user attribute as a single argument.
<?php
class Test {
function insertUser() {
// gets the number of parameters
$numArgs = func_num_args();
// make decisions based on the arguments number
if ($numArgs == 1) {
// if it's only one argument, we suppose that it is an array with user info
// gets the first argument
$user = func_get_arg(0);
// checks if it really is an array
if (is_array($user)) {
// here you should check if the array contains all necessary fields
// adds the user
echo "User added.<br/>";
echo "ID: " . $user["id"] . "<br/>";
echo "NAME: " . $user["name"] . "<br/>";
echo "EMAIL: " . $user["email"] . "<br/>";
} else {
// generates an error if argument is not an array
echo "Argument is not an array: " . $user . ".<br/>";
}
} else if ($numArgs == 3) {
// if the function receives 3 arguments, we assume that they
// are 'id', 'name' and 'email' respectively
// inserts the user into the system
echo "User added.<br/>";
echo "ID: " . func_get_arg(0) . "<br/>";
echo "NAME: " . func_get_arg(1) . "<br/>";
echo "EMAIL: " . func_get_arg(2) . "<br/>";
} else {
// if the number of arguments is different from 1 and 3
// an error will be generated
echo "Wrong argument number.<br/>";
echo "Arguments received: " . func_num_args();
}
}
}
// creates an Test object
$objTest = new Teste();
// inserts an user passing an array with all his info
$objTest->insertUser(array("id" => 1, "name" => "George W. Bush", "email" => "jackass@whitehouse.gov"));
echo "<br/>";
// inserts an user providing each attribute as a single argument
$objTest->insertUser(2, "Vicente Fox", "iloveusa@disney.com");
echo "<br/>";
// this will generate an error, because only 2 arguments were passed
$objTest->insertUser(3, "Tony Blair");
?>
Just adding a note to JARED's Note.
func_num_args() works if and only if called from within a function definition BECAUSE it calculates the number of arguments sent while function calling. That is why it gives
'1' in helloWorld("HelloWorld!") and '2' in helloWorld("HelloWorld!", "HowdyWorld!") - There is nothing to do with DEFAULT args.
If you call the same function as helloWorld(); "No args passed"
It will give a warning for wrong function call ("Warning: Missing argument 1 for helloWorld()") and the result of func_num_args() will be '0'.
This function comes in extremely handy in OO Classes. My focus is currently PHP 4, but this technique probably works just as well in PHP 5.
<?php
Class foo {
// constructor, other methods, etc
function somedata($somedata = '') {
if (func_num_args() > 0) {
$this->somedata = $somedata;
}
return $this->somedata;
}
}
?>
This allows for a default value to be set, while not requiring the parameter. (Yes, I'm aware that it only warns when you do, but I think this is a little cleaner)
Just a note for anyone wondering. This function doesn't include params that have a default value, unless you pass one in to overwrite the default param value. Not sure if that makes sense, so here's an example:
<?php
function helloWorld($ArgA, $ArgB="HelloWorld!") {
return func_num_args();
}
// The following will return 1
$Returns1 = helloWorld("HelloWorld!");
// The following will return 2
$Returns2 = helloWorld("HelloWorld!", "HowdyWorld!");
?>
func_num_args() can be used in conjunction with named arguments, also. For example:
<?php
function DebugShow( $label, $value ) {
echo "# " . $label ;
if ( func_num_args() > 1 ) echo " = " . $value ;
echo "<br>";
}
?>
If you want to pass the parameters on intact to another function, use func_get_args and call_user_func_array (careful - this one is only available in recent PHP versions). For example:
<?php
/* Print an HTML tag. This accepts a variable number of arguments:
the first should be the name of the tag, followed by pairs of
arguments that describe keys and values. The values are printed
with surrounding double quote characters. */
function printTag() {
$numArgs = func_num_args();
if ($numArgs < 1) die("printTag given no arguments");
echo "<" . func_get_arg(0);
for ($i = 1; $i < $numArgs; $i+=2) {
echo " " . func_get_arg($i);
if ($i+1 < $numArgs)
echo "=\"" . func_get_arg($i+1) . "\"";
}
echo ">";
}
/* Print an HTML tag with a newline on the end */
function printTagNL() {
$args = func_get_args();
call_user_func_array("printTag", $args);
echo "\n";
}
printTagNL("input", "type", "hidden", "name", "SORTORDER", "value", $columnNo);
?>
The idea of func_get_args() is to construct functions of variable number of parameters like
<?php
function var_param_func(){
if(func_num_args()==0){
//do one thing
}
if(func_num_args()==1)
//do another thing
//get the args with func_get_args()
}
}
?>
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