1 <?php
 2 
 3 class Stack{
 4     const MAXSIZE = 4;// 栈最大容量
 5     private $top = -1;
 6     private $stack = array();// 利用数组存储数据
 7 
 8     public function __construct(){
 9         $this->stack = array();
10     }
11 
12     // 入栈
13     public function push($ele){
14         if ($this->top >= self::MAXSIZE-1){
15             echo 'stack is full...';
16             return false;
17         }
18         $this->stack[++$this->top] = $ele;// 此处必须是++i，先计算再使用
19     }
20 
21     // 出栈，返回出栈元素
22     public function pop(){
23         if ($this->top == -1){
24             echo 'stack is empty...';
25             return false;
26         }
27         $ele = $this->stack[$this->top];
28         unset($this->stack[$this->top--]);// 此处必须是i--，先使用再计算（注意出栈和入栈的区别）
29         return $ele;
30     }
31 
32     // 遍历栈
33     public function show(){
34         if ($this->top == -1){
35             echo 'stack is empty...';
36             return false;
37         }
38         for($i=$this->top; $i>-1; $i--){
39             echo $this->stack[$i].'<br/>';
40         }
41     }
42 
43 }
44 
45 $stack = new Stack;
46 $stack->push(1);
47 $stack->push(2);
48 $stack->push(3);
49 $stack->push(4);
50 
51 //print_r($stack);
52 $stack->show();
53 
54 
55 $a = $stack->pop();
56 $a = $stack->pop();
57 $a = $stack->pop();
58 
59 $stack->show();