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array_walk

(PHP 4, PHP 5)

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

Description

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

Returns TRUE on success or FALSE on failure.

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

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().

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.

Note: Passing the key and userdata to funcname 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.

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 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(), create_function(), list(), foreach, each(), call_user_func_array(), and array_map(), and information about the callback type.