pre=linkList
current=linkList
while current!=null
  if current->data==current->next->data
    value=current->data
    while value==current->next->data
      current=current->next
    pre->next=current->next
  pre=pre->next
  current=current->next
return linkList

<?php
class Node{
    public $data;
    public $next;
    public function __construct($data=""){
        $this->data=$data;
    }  
}
//构造一个带重复的链表
$linkList=new Node();
$linkList->next=null;
$temp=$linkList;
$node1=new Node(2);
$temp->next=$node1;
$temp=$node1;
$node2=new Node(2);
$temp->next=$node2;
$temp=$node2;
$node3=new Node(3);
$temp->next=$node3;
$temp=$node3;
$node4=new Node(3);
$temp->next=$node4;
$temp=$node4;
$node5=new Node(4);
$temp->next=$node5;
$node5->next=null;
function deleteDuplication($pHead){
    $pre=$pHead->next;//当前都指向第一个结点
    $current=$pHead->next;//当前结点是第一个结点
    while($current!=null){
        //如果当前结点值和当前结点的下一个结点值相同
        if($current->next!=null && $current->data==$current->next->data){
            //保存当前结点值
            $val=$current->data;
            //当前结点往后移直到和下一个结点值不相等
            while($current->next!=null && $val==$current->next->data){
                $current=$current->next;
            }  
            //前一个指针next直接指向当前结点的next
            $pre->next=$current->next;
        }  
        //两个指针同时后移
        $pre=$pre->next;
        $current=$current->next;
    }
    return $pHead;
}
var_dump($linkList);
$result=deleteDuplication($linkList);
var_dump($result);

object(Node)#1 (2) {
 ["data"]=>
 string(0) ""
 ["next"]=>
 object(Node)#2 (2) {
  ["data"]=>
  int(2)
  ["next"]=>
  object(Node)#3 (2) {
   ["data"]=>
   int(2)
   ["next"]=>
   object(Node)#4 (2) {
    ["data"]=>
    int(3)
    ["next"]=>
    object(Node)#5 (2) {
     ["data"]=>
     int(3)
     ["next"]=>
     object(Node)#6 (2) {
      ["data"]=>
      int(4)
      ["next"]=>
      NULL
     }
    }
   }
  }
 }
}
object(Node)#1 (2) {
 ["data"]=>
 string(0) ""
 ["next"]=>
 object(Node)#2 (2) {
  ["data"]=>
  int(2)
  ["next"]=>
  object(Node)#4 (2) {
   ["data"]=>
   int(3)
   ["next"]=>
   object(Node)#6 (2) {
    ["data"]=>
    int(4)
    ["next"]=>
    NULL
   }
  }
 }
}