func_get_arg()

(PHP 4, PHP 5, PHP 7)

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

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

Example #1func_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);
?>

Example #2func_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

Example #3func_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：

注释

Note:

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。

Note:

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。

Note: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

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));
?>

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.

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 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.