array_intersect_key Computes the intersection of arrays using keys for comparison &reftitle.description; arrayarray_intersect_key arrayarray1 arrayarray2 array... array_intersect_key returns an array containing all the entries of array1 which have keys that are present in all the arguments. &reftitle.parameters; array1 The array with master keys to check. array2 An array to compare keys against. ... A variable list of arrays to compare. &reftitle.returnvalues; Returns an associative array containing all the entries of array1 which have keys that are present in all arguments. &reftitle.examples; 1, 'red' => 2, 'green' => 3, 'purple' => 4); $array2 = array('green' => 5, 'blue' => 6, 'yellow' => 7, 'cyan' => 8); var_dump(array_intersect_key($array1, $array2)); ?> ]]> &example.outputs; int(1) ["green"]=> int(3) } ]]> In our example you see that only the keys 'blue' and 'green' are present in both arrays and thus returned. Also notice that the values for the keys 'blue' and 'green' differ between the two arrays. A match still occurs because only the keys are checked. The values returned are those of array1. The two keys from the key => value pairs are considered equal only if (string) $key1 === (string) $key2 . In other words a strict type check is executed so the string representation must be the same. &reftitle.seealso; array_diff array_udiff array_diff_assoc array_diff_uassoc array_udiff_assoc array_udiff_uassoc array_diff_key array_diff_ukey array_intersect array_intersect_assoc array_intersect_uassoc array_intersect_ukey