array_filter
(PHP 4 >= 4.0.6, PHP 5, PHP 7, PHP 8)
array_filter — 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
-
array -
The array to iterate over
-
callback -
The callback function to use
If no
callbackis supplied, all empty entries ofarraywill 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 tocallbackinstead of the value -
ARRAY_FILTER_USE_BOTH- pass both value and key as arguments tocallbackinstead of the value
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.
|
| 8.0.0 |
If callback expects a parameter to be passed
by reference, this function will now emit an E_WARNING.
|
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
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_intersect() - Computes the intersection of arrays
- 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
