php实现链表的方法是什么

class Node{
    public $val;
    public $next;
    function __construct($val=null){
        $this->val = $val;
        $this->next = null;
    }
}

class MyLinkedList {
    public $dummyhead; //定义一个虚拟的头结点
    public $size;
  
    function __construct() {
        $this->dummyhead = new Node(); 
        $this->size = 0;
    }
  
 
    function get($index) {
        if($index < 0 || $index >= $this->size)
            return -1;
        $cur = $this->dummyhead;
        for($i = 0; $i < $index; $i++){
            $cur = $cur->next;
        }
        return $cur->next->val;
    }
  
    function addAtHead($val) {
        $this->addAtIndex(0,$val);
    }
  
  
    function addAtTail($val) {
        $this->addAtIndex($this->size,$val);
    }
  
    function addAtIndex($index, $val) {
        if($index < 0 || $index > $this->size)
            return;
        $cur = $this->dummyhead;
        for($i = 0; $i < $index; $i++){
            $cur = $cur->next;
        }
        $node = new Node($val);
        $node->next = $cur->next;
        $cur->next = $node;
        $this->size++;
    }
  
    function deleteAtIndex($index) {
        if($index < 0 || $index >= $this->size)
            return;
        $cur = $this->dummyhead;
        for($i = 0; $i < $index; $i++){
            $cur = $cur->next;
        }
        $cur->next = $cur->next->next;
        $this->size--;
    }
}