array_diff_key()

array_diff_key() — Computes the difference of arrays using keys for comparison.

Built-in function of PHP 8.5. The manual lists it as available in PHP 5 >= 5.1.0, 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

Compares the keys from array against the keys from arrays and returns the difference. This function is like array_diff() except the comparison is done on the keys instead of the values.

Signature

array_diff_key(array $array, array ...$arrays): array

Parameters

Return value

Returns an array containing all the entries from array whose keys are absent from all of the other arrays.

Example

A runnable snippet:

$array1 = array('blue' => 1, 'red' => 2, 'green' => 3, 'purple' => 4); $array2 = array('green' => 5, 'yellow' => 7, 'cyan' => 8); var_dump(array_diff_key($array1, $array2));

Output:

array(3) { ["blue"]=> int(1) ["red"]=> int(2) ["purple"]=> int(4) }

Changelog

See also

array_diff(), array_udiff(), array_diff_assoc(), array_diff_uassoc(), array_udiff_assoc(), array_udiff_uassoc(), array_diff_ukey(), array_intersect(), array_intersect_assoc(), array_intersect_uassoc(), array_intersect_key(), array_intersect_ukey()

All PHP 8.5 built-in functions

Reference card built from the PHP manual page array_diff_key() (PHP documentation, CC BY 3.0). The page is generated from the manual, so the wording of the parameter and return value text follows php.net.