array_walk_recursive
array
Array Functions
PHP Manual

# array_walk

(PHP 4, PHP 5)

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

### Description

bool array_walk ( array `&$array` , callable `$callback` [, mixed `$userdata` = `NULL` ] )

Applies the user-defined `callback` function 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.

`callback`

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

  > Note:

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

  > Note:

  > Many internal functions (for example strtolower()) will throw a warning if more than the expected number of argument are passed in and are not usable directly as a `callback`.

  Only the values of the `array` may potentially be changed; its structure cannot be altered, i.e., the programmer cannot add, unset or reorder elements. If the callback does not respect this requirement, 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`.

### Return Values

Returns `TRUE` on success or `FALSE` on failure.

### Errors/Exceptions

If function `callback` requires more parameters than given to it, an error of level E_WARNING will be generated each time array_walk() calls `callback`.

### 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

### See Also

- array_walk_recursive() - Apply a user function recursively to every member of an array
- iterator_apply() - Call a function for every element in an iterator
- list() - Assign variables as if they were an array
- each() - Return the current key and value pair from an array and advance the array cursor
- call_user_func_array() - Call a callback with an array of parameters
- array_map() - Applies the callback to the elements of the given arrays
- information about the callback type
- foreach

array_walk_recursive
array
Array Functions
PHP Manual