array_filter

(PHP 4 >= 4.0.6, PHP 5, PHP 7)

array_filterFilters elements of an array using a callback function


Description

array_filter ( array $array [, callable|null $callback = NULL [, int $mode = 0 ]] ) : array

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.

Array keys are preserved, and may result in gaps if the array was indexed. The result array can be reindexed using the array_values() function.


Parameters

array

The array to iterate over

callback

The callback function to use

If no callback is supplied, all empty entries of array will be removed. See empty() for how PHP defines empty in this case.

mode

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 Values

Returns the filtered array.


Changelog

Version Description
8.0.0 callback is nullable now.
5.6.0 Added optional mode parameter and constants

ARRAY_FILTER_USE_KEY and ARRAY_FILTER_USE_BOTH


Examples

Example #1 array_filter() example

<?phpfunction 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"));?>

The above example will output:


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

Example #2 array_filter() without callback

<?php$entry = [    0 => 'foo',    1 => false,    2 => -1,    3 => null,    4 => ,    5 => '0',    6 => 0,];print_r(array_filter($entry));?>

The above example will output:


Array
(
    [0] => foo
    [2] => -1
)

Example #3 array_filter() with mode

<?php$arr = ['a' => 1, 'b' => 2, 'c' => 3, 'd' => 4];var_dump(array_filter($arr, function($k) {    return $k == 'b';}, ARRAY_FILTER_USE_KEY));var_dump(array_filter($arr, function($v, $k) {    return $k == 'b' || $v == 4;}, ARRAY_FILTER_USE_BOTH));?>

The above example will output:


array(1) {
  ["b"]=>
  int(2)
}
array(2) {
  ["b"]=>
  int(2)
  ["d"]=>
  int(4)
}

Notes

Caution If the array is changed from the callback function (e.g. element added, deleted or unset) the behavior of this function is undefined.


See Also

  • array_map() - Applies the callback to the elements of the given arrays
  • array_reduce() - Iteratively reduce the array to a single value using a callback function
  • array_walk() - Apply a user supplied function to every member of an array