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array_walk

Description

The array_walk of Array for PHP apply a user supplied function to every member of an array.

Syntax

array_walk(array|object &$array, callable $callback, mixed $arg = null): bool

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.

arg

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

Return

Returns true.

Examples

1 · array callback

<?

function myfunction(&$value, $key)
{
    return $value .= "s";
}

$array = array("a" => "orange", "b" => "banana", "c" => "apple", "d" => "lemon");
$callback = "myfunction";

array_walk($array, $callback);

print_r($array);

?>
Array
(
    [a] => oranges
    [b] => bananas
    [c] => apples
    [d] => lemons
)

2 · arg

<?

function myfunction(&$value, $key, $arg)
{
    return $value = "$arg: $value" . "s";
}

$array = array("a" => "orange", "b" => "banana", "c" => "apple", "d" => "lemon");
$callback = "myfunction";
$arg = "fruit";

array_walk($array, $callback, $arg);

print_r($array);

?>
Array
(
    [a] => fruit: oranges
    [b] => fruit: bananas
    [c] => fruit: apples
    [d] => fruit: lemons
)
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