Online PHP editor | output for IOvBR

<?php function orderBeforeArray($name, $destination, $list) { // reindex the array so there are no gaps $list = array_values($list); $oldpos = array_search($name, $list); if (false === $oldpos) { throw new ItemNotFoundException("$name is not a child of this node"); } if ($destination == null) { // null means move to end unset($list[$oldpos]); $list[] = $name; } else { // insert before element $destination $newpos = array_search($destination, $list); if ($newpos === false) { throw new ItemNotFoundException("$destination is not a child of this node"); } if ($oldpos < $newpos) { // we first unset, the position will change by one $newpos--; } unset($list[$oldpos]); array_splice($list, $newpos, 0, $name); } return $list; } $old = ['one', 'two', 'three', 'four']; $new = ['one', 'three', 'two']; $reorders = []; //check for deleted items $newIndex = array_flip($new); foreach ($old as $key => $value) { if (!isset($newIndex[$value])) { unset($old[$key]); } } // reindex the arrays to avoid holes in the indexes $old = array_values($old); $new = array_values($new); $len = count($new) - 1; $oldIndex = array_flip($old); //go backwards on the new node order and arrange them this way for ($i = $len; $i >= 0; $i--) { //get the name of the child node $current = $new[$i]; //check if it's not the last node if (isset($new[$i + 1])) { // get the name of the next node $next = $new[$i + 1]; //if in the old order $c and next are not neighbors already, do the reorder command if ($oldIndex[$current] + 1 != $oldIndex[$next]) { $reorders[$current] = $next; $old = orderBeforeArray($current, $next, $old); $oldIndex = array_flip($old); } } else { //check if it's not already at the end of the nodes if ($oldIndex[$current] != $len) { $reorders[$current] = null; $old = orderBeforeArray($current, null, $old); $oldIndex = array_flip($old); } } } var_dump($reorders);