func_get_arg
(PHP 4, PHP 5)
func_get_arg — Return an item from the argument list
Description
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: $numargs<br />\n";
if ($numargs >= 2) {
echo "Second argument is: " . func_get_arg(1) . "<br />\n";
}
}
foo (1, 2, 3);
?>
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.
See Also
- func_get_args() - Returns an array comprising a function's argument list
- func_num_args() - Returns the number of arguments passed to the function
Коментарии
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.
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.
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.
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));
?>
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'