array_filter()

array_filter() — Filters elements of an array using a callback function.

Built-in function of PHP 8.5. The manual lists it as available in PHP 4 >= 4.0.6, PHP 5, PHP 7, PHP 8. This page is the reference card: signature, parameters and return value, plus the changelog and the example the manual provides.

What it does

Iterates over each value in the array passing them to the callback function. If the callback function returns true, the current value from array is returned into the result array.

Signature

array_filter(array $array, ?callable $callback = null, int $mode = 0): array

Parameters

Parameter	Type	What it takes
$array	array	The array to iterate over
$callback	?callable	The callback function to use
$mode	int	Flag determining what arguments are sent to callback: ARRAY_FILTER_USE_KEY - pass key as the only argument to callback instead of the value ARRAY_FILTER_USE_BOTH - pass both value and key as arguments to callback instead of the value Default is 0 which will pass value as the only argument to callback instead.

Return value

Returns the filtered array.

Example

A runnable snippet:

function odd($var) { // returns whether the input integer is odd return $var & 1; } function even($var) { // returns whether the input integer is even return !($var & 1); } $array1 = ['a' => 1, 'b' => 2, 'c' => 3, 'd' => 4, 'e' => 5]; $array2 = [6, 7, 8, 9, 10, 11, 12]; echo "Odd :\n"; print_r(array_filter($array1, "odd")); echo "Even:\n"; print_r(array_filter($array2, "even"));

Output:

Odd : Array ( [a] => 1 [c] => 3 [e] => 5 ) Even: Array ( [0] => 6 [2] => 8 [4] => 10 [6] => 12 )

Changelog

Version	Change
8.0.0	callback is nullable now.
8.0.0	If callback expects a parameter to be passed by reference, this function will now emit an E_WARNING.