array_filter

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

array_filter — Filters 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

<?php
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"));
?>

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

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Licensed under the Creative Commons Attribution License v3.0 or later.
https://www.php.net/manual/en/function.array-filter.php