func_get_arg
(PHP 4, PHP 5)
func_get_arg — Return an item from the argument list
说明
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.
参数
- arg_num
-
The argument offset. Function arguments are counted starting from zero.
返回值
Returns the specified argument, or FALSE on error.
更新日志
| 版本 | 说明 |
|---|---|
| 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. |
错误/异常
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.
范例
Example #1 func_get_arg() example
<?php
function foo()
{
$numargs = func_num_args();
echo "Number of arguments: $numargs<br />
";
if ($numargs >= 2) {
echo "Second argument is: " . func_get_arg(1) . "<br />
";
}
}
foo (1, 2, 3);
?>
Example #2 func_get_arg() example before and
after PHP 5.3
Output previous to PHP 5.3:
Output in PHP 5.3 and later:
test.php
<?php
function foo() {
include './fga.inc';
}
foo('First arg', 'Second arg');
?>
fga.php
<?php
$arg = func_get_arg(1);
var_export($arg);
?>
'Second arg'
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 以上例程会输出：
<?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);
?>
As passed : 'bar'
After change : 'bar'
As passed : 'bar'
After change : 'baz'
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:
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.
参见
- func_get_args() - Returns an array comprising a function's argument list
- func_num_args() - Returns the number of arguments passed to the function
