array_diff_ukey Computes the difference of arrays using a callback function on the keys for comparison &reftitle.description; arrayarray_diff_ukey arrayarray arrayarrays callablekey_compare_func 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. Unlike array_diff_key a user supplied callback function is used for the indices comparison, not internal function. &reftitle.parameters; array The array to compare from arrays Arrays to compare against key_compare_func &return.callbacksort; &callback.cmp; &reftitle.returnvalues; Returns an array containing all the entries from array 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