array_walk

(PHP 3>= 3.0.3, PHP 4 )

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

Description

int array_walk ( array array, string func [, mixed userdata])

Applies the user-defined function func to each element of the array array. Typically, func takes on two parameters. The array parameter's value being the first, and the key/index second. If the optional userdata parameter is supplied, it will be passed as the third parameter to function func.

func must be a user-defined function, not a built-in PHP function such as strtolower() or stripslashes(). The user-defined function can use built-in PHP functions.

Note: Instead of a function name, an array containing an object reference and a method name can also be supplied.

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

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

Note: Passing the key and userdata to func was added in 4.0.0

array_walk() is not affected by the internal array pointer of array. array_walk() will walk through the entire array regardless of pointer position. To reset the pointer, use reset(). In PHP 3, array_walk() resets the pointer.

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.

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 printout of the program above will be:
Before ...:
d. lemon
a. orange
b. banana
c. apple
... and after:
d. fruit: lemon
a. fruit: orange
b. fruit: banana
c. fruit: apple

See also list(), foreach, each(), and call_user_func_array().