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func_get_arg

(PHP 4, PHP 5, PHP 7, PHP 8)

func_get_arg — 返回参数列表的某一项

说明

func_get_arg(int $arg_num): mixed

从用户自定义函数的参数列表中获取某个指定的参数。

该函数可以配合 func_get_args() 和 func_num_args() 一起使用，从而使得用户自定义函数可以接受自定义个数的参数列表。

参数

arg_num: 参数的偏移量。函数的参数是从0开始计数的。

返回值

返回指定的参数，错误则返回 false 。

更新日志

版本	说明
5.3.0	该函数可以在参数列表中使用。
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`. （不知道如何翻译跟好，直接参考例2即可明白）

错误／异常

当在自定义函数的外面调用的该函数的时候会发出一个警告，或者是当 arg_num 比实际传入的参数的数目大的时候也会发出一个警告。

范例

示例 #1 func_get_arg() 例子


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

foo (1, 2, 3);
?>

示例 #2 func_get_arg() PHP 5.3 前后对比的例子


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

foo('First arg', 'Second arg');
?>

fga.inc
<?php

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

?>

PHP 5.3 版本之前的输出：

'Second arg'

PHP 5.3 和之后的版本的输出:

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

示例 #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);
?>

以上例程会输出：

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

注释

注意:
因为函数依赖于当前作用域以确定参数的细节，所以在 5.3.0 以前的版本中不能用作函数的参数。如必须传递此值时，可将结果赋与一个变量，然后用此变量进行传递。

注意:
如果参数以引用方式传递，函数对该参数的任何改变将在函数返回后保留。As of PHP 7 the current values will also be returned if the arguments are passed by value.

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

参见

func_get_args() - 返回一个包含函数参数列表的数组
func_num_args() - Returns the number of arguments passed to the function

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User Contributed Notes 5 notes

down

beta3designs [at] gmail [dot] com ¶

12 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));
?>

down

gordon at abetz-rouse dot com dot au ¶

2 years ago


This function may work differently from php5 to php7, in the latter it seems to reference the variable, while in php5 it returns the original argument.
I have confirmed with the versions below, but this will require further confirmation as to whether this is a 5 versus 7 issue.

function test( $test ){

    $test = '123';

    echo func_get_arg(0);

}

test( '321' );

//in php 5.5.9, this script will write '321'
//in php 7.0.33, this script will write '123'

down

mightye (at) mightye (dot) org ¶

18 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.

down

-4

mw atto lanfear dotto com ¶

17 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.

down

-5

anders at ingemann dot fakestuff dot de ¶

18 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.

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