SplDoublyLinkedList::unshift (PHP 5 >= 5.3.0, PHP 7, PHP 8)SplDoublyLinkedList::unshift — Prepends the doubly linked list with an element 说明 public SplDoublyLinkedList::unshift(mixed $value): void Prepends value at the beginning of the doubly linked list. 参数 value The value to unshift. 返回值 没有返回值。