PHP reverse list

rev.php

/**
 * Definition for a singly-linked list.
 * class ListNode {
 *     public $val = 0;
 *     public $next = null;
 *     function __construct($val = 0, $next = null) {
 *         $this->val = $val;
 *         $this->next = $next;
 *     }
 * }
 */
class Solution {

    /**
     * @param ListNode $head
     * @return ListNode
     */
    /* iterative solution
    function reverseList($head) {
        $node = $head;
        $reversed = null;
            
        while ($node != null) {
            $next = $node->next;
            $node->next = $reversed;
            $reversed = $node;
            $node = $next;
        }
        
        return $reversed;
    } 
    */
    
    /* recursive solution */
    function reverseList($head) {
        return $this->doReverseList($head, null);
    }
        
    function doReverseList($head, $list) {
        if ($head == null) {
            return $list;
        }
        
        $next = $head->next;
        $head->next = $list;
        return $this->doReverseList($next, $head);
    }
}