$a = new SplDoublyLinkedList;$arr=[1,2,3,4,5,6,7,8,9];for($i=0;$i<count($arr);$i++){ $a->add($i,$arr[$i]);}print_r($a);//Output:SplDoublyLinkedList Object( [flags:SplDoublyLinkedList:private] => 0 [dllist:SplDoublyLinkedList:private] => Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 [5] => 6 [6] => 7 [7] => 8 [8] => 9 ))