array_diff_ukey Computes the difference of arrays using a callback function on the keys for comparison &reftitle.description; arrayarray_diff_ukey arrayarray1 arrayarray2 array ... callbackkey_compare_func Compares the keys from array1 against the keys from array2 and returns the difference. This function is like array_diff except the comparison is done on the keys instead of the values. Unlike array_diff_key an user supplied callback function is used for the indices comparison, not internal function. &reftitle.parameters; array1 The array to compare from array2 An array to compare against ... More arrays to compare against key_compare_func callback function to use. The callback function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second. &reftitle.returnvalues; Returns an array containing all the entries from array1 that are not present in any of the other arrays. &reftitle.examples; $key2) return 1; else return -1; } $array1 = array('blue' => 1, 'red' => 2, 'green' => 3, 'purple' => 4); $array2 = array('green' => 5, 'blue' => 6, 'yellow' => 7, 'cyan' => 8); var_dump(array_diff_ukey($array1, $array2, 'key_compare_func')); ?> ]]> &example.outputs; int(2) ["purple"]=> int(4) } ]]> &reftitle.notes; This function only checks one dimension of a n-dimensional array. Of course you can check deeper dimensions by using array_diff_ukey($array1[0], $array2[0], 'callback_func');. &reftitle.seealso; array_diff array_udiff array_diff_assoc array_diff_uassoc array_udiff_assoc array_udiff_uassoc array_diff_key array_intersect array_intersect_assoc array_intersect_uassoc array_intersect_key array_intersect_ukey