array_filter
(PHP 4 >= 4.0.6, PHP 5, PHP 7, PHP 8)
Filters elements of an array using a callback function
Description
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
arrayThe array to iterate over
callbackThe callback function to use
If no
callbackis supplied, all empty entries ofarraywill be removed. Seeempty()for how PHP defines empty in this case.modeFlag determining what arguments are sent to
callback:ARRAY_FILTER_USE_KEY- pass key as the only argument tocallbackinstead of the valueARRAY_FILTER_USE_BOTH- pass both value and key as arguments tocallbackinstead of the value
Default is
0which will pass value as the only argument tocallbackinstead.
Return Values
Returns the filtered array.
Changelog
| Version | Description |
|---|---|
| 8.0.0 | callback is nullable now. |
Examples
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
)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
)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
If the array is changed from the callback function (e.g. element added or unset) the behavior of this function is undefined.