DevConf 2015

func_get_arg

(PHP 4, PHP 5)

func_get_argReturn an item from the argument list

Description

mixed func_get_arg ( int $arg_num )

Gets the specified argument from a user-defined function's argument list.

This function may be used in conjunction with func_get_args() and func_num_args() to allow user-defined functions to accept variable-length argument lists.

Parameters

arg_num

The argument offset. Function arguments are counted starting from zero.

Return Values

Returns the specified argument, or FALSE on error.

Changelog

Version Description
5.3.0 This function can now be used in parameter lists.
5.3.0 If this function is called from the outermost scope of a file which has been included by calling include or require from within a function in the calling file, it now generates a warning and returns FALSE.

Errors/Exceptions

Generates a warning if called from outside of a user-defined function, or if arg_num is greater than the number of arguments actually passed.

Examples

Example #1 func_get_arg() example

<?php
function foo()
{
     
$numargs func_num_args();
     echo 
"Number of arguments: $numargs\n";
     if (
$numargs >= 2) {
         echo 
"Second argument is: " func_get_arg(1) . "\n";
     }
}

foo(123);
?>

The above example will output:

Number of arguments: 3
Second argument is: 2

Example #2 func_get_arg() example before and after PHP 5.3

test.php
<?php
function foo() {
    include 
'./fga.inc';
}

foo('First arg''Second arg');
?>

fga.inc
<?php

$arg 
func_get_arg(1);
var_export($arg);

?>

Output previous to PHP 5.3:

'Second arg'

Output in PHP 5.3 and later:

Warning: func_get_arg():  Called from the global scope - no function
context in /home/torben/Desktop/code/ml/fga.inc on line 3
false

Example #3 func_get_arg() example of byref and byval arguments

<?php
function byVal($arg) {
    echo 
'As passed     : 'var_export(func_get_arg(0)), PHP_EOL;
    
$arg 'baz';
    echo 
'After change  : 'var_export(func_get_arg(0)), PHP_EOL;
}

function 
byRef(&$arg) {
    echo 
'As passed     : 'var_export(func_get_arg(0)), PHP_EOL;
    
$arg 'baz';
    echo 
'After change  : 'var_export(func_get_arg(0)), PHP_EOL;
}

$arg 'bar';
byVal($arg);
byRef($arg);
?>

The above example will output:


As passed : 'bar'
After change : 'bar'
As passed : 'bar'
After change : 'baz'

Notes

Note:

Because this function depends on the current scope to determine parameter details, it cannot be used as a function parameter in versions prior to 5.3.0. If this value must be passed, the results should be assigned to a variable, and that variable should be passed.

Note:

If the arguments are passed by reference, any changes to the arguments will be reflected in the values returned by this function.

Note: This function returns a copy of the passed arguments only, and does not account for default (non-passed) arguments.

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User Contributed Notes 4 notes

up
1
beta3designs [at] gmail [dot] com
5 years ago
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));
?>
up
0
anders at ingemann dot fakestuff dot de
10 years ago
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.
up
-1
mightye (at) mightye (dot) org
11 years ago
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.
up
-1
mw atto lanfear dotto com
10 years ago
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.
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