$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]);
}
$serialize=serialize($a);
echo $serialize;
echo PHP_EOL,PHP_EOL;
$unserialze=unserialize($serialize);
print_r($unserialze);