PHP: array_walk function - Apply a user function to every member of an array

Description

bool array_walk ( array &$array , callback $funcname [, mixed $userdata ] )

Applies the user-defined function funcname to each element of the array array.

array_walk() is not affected by the internal array pointer of array . array_walk() will walk through the entire array regardless of pointer position.

Parameters

array

The input array.

funcname

Typically, funcname takes on two parameters. The array parameter's value being the first, and the key/index second.

Note: If funcname needs to be working with the actual values of the array, specify the first parameter of funcname as a reference. Then, any changes made to those elements will be made in the original array itself.

Users may not change the array itself from the callback function. e.g. Add/delete elements, unset elements, etc. If the array that array_walk() is applied to is changed, the behavior of this function is undefined, and unpredictable.

userdata

If the optional userdata parameter is supplied, it will be passed as the third parameter to the callback funcname .

Return Values

Returns TRUE on success or FALSE on failure.

Errors/Exceptions

If function funcname requires more parameters than given to it, an error of level E_WARNING will be generated each time array_walk() calls funcname . These warnings may be suppressed by prepending the PHP error operator @ to the array_walk() call, or by using error_reporting().

ChangeLog

Version	Description
4.0.0	Passing the key and `userdata` to `funcname` was added.

Examples

Example #1 array_walk() example


<?php
$fruits = array("d" => "lemon", "a" => "orange", "b" => "banana", "c" => "apple");

function test_alter(&$item1, $key, $prefix)
{
    $item1 = "$prefix: $item1";
}

function test_print($item2, $key)
{
    echo "$key. $item2<br />\n";
}

echo "Before ...:\n";
array_walk($fruits, 'test_print');

array_walk($fruits, 'test_alter', 'fruit');
echo "... and after:\n";

array_walk($fruits, 'test_print');
?>

The above example will output:

Before ...:
d. lemon
a. orange
b. banana
c. apple
... and after:
d. fruit: lemon
a. fruit: orange
b. fruit: banana
c. fruit: apple

array_walk