multidimensional array difference php

Question

I have two multidimensional arrays and I want the difference. For eg. I have taken two-dimensional two arrays below

$array1 = Array (
       [a1] => Array         


        

Answer 1

Almost a copy of @bernhardh's answer but posting here because my edit was rejected. Uses + instead of array_merge as array_merge will reindex array causing issues with indexed arrays.

/**
 * Given 2 arrays see what has changed when comparing defaults to the new values.
 *
 * @param array $defaults
 *   Array of default values.
  * @param mixed $new_values
 *   Array of new values.
 *
 * @return array
 *   Nested array strucutre; only the diff.
 */
function array_diff_multi(array $defaults, $new_values) {
  $result = array();

  foreach ($defaults as $key => $val) {
    if (is_array($val) && isset($new_values[$key])) {
      $tmp = array_diff_multi($val, $new_values[$key]);
      if ($tmp) {
        $result[$key] = $tmp;
      }
    }
    elseif (!isset($new_values[$key])) {
      $result[$key] = NULL;
    }
    elseif ($val != $new_values[$key]) {
      $result[$key] = $new_values[$key];
    }
    if (isset($new_values[$key])) {
      unset($new_values[$key]);
    }
  }

  $result = $result + $new_values;
  return $result;
}