1 
     top = 0;18             foreach($a as $val) {19                 $this->push($val);20             }21         }22 23         public function push($i) {24             $node = new Node();25             $node->data = $i;26 27             #此处设置每个节点的min值，设置方法为若栈为空，当前元素data则为当前节点的min28             #若栈非空，则当前元素data与前一个节点的min值比较，取其小者作为当前节点的min29             if ($this->top == 0) {30                 $min = $node->data;31             } else {32                 $min = $this->data[$this->top - 1]->min < $node->data ? $this->data[$this->top - 1]->min : $node->data;33             }34 35             $node->min = $min;36             $this->data[] = $node;37             $this->top++;38             return $node;39         }40 41         public function pop() {42             $r = $this->data[--$this->top];43             unset($this->data[$this->top]);44             return $r;45         }46 47         public function get_min() {48             return $this->data[$this->top - 1]->min;49         }50     }51 52     $a = array(5, 7, 3, 8, 9, 1, 2);53     $min_stack = new Min_Stack($a);54     echo "Min : {
   $min_stack->get_min()} 
";55     print_r($min_stack);56     echo "
 Pop : {
   $min_stack->pop()->data}
";57     print_r($min_stack); 58 ?>

Min : 1 

Min_Stack Object ( [data:Min_Stack:private] => Array ( [0] => Node Object ( [data] => 5 [min] => 5 ) [1] => Node Object ( [data] => 7 [min] => 5 ) [2] => Node Object ( [data] => 3 [min] => 3 ) [3] => Node Object ( [data] => 8 [min] => 3 ) [4] => Node Object ( [data] => 9 [min] => 3 ) [5] => Node Object ( [data] => 1 [min] => 1 ) [6] => Node Object ( [data] => 2 [min] => 1 ) ) [top:Min_Stack:private] => 7 ) 

Pop : 2

Pop : 1

Min : 3 

Min_Stack Object ( [data:Min_Stack:private] => Array ( [0] => Node Object ( [data] => 5 [min] => 5 ) [1] => Node Object ( [data] => 7 [min] => 5 ) [2] => Node Object ( [data] => 3 [min] => 3 ) [3] => Node Object ( [data] => 8 [min] => 3 ) [4] => Node Object ( [data] => 9 [min] => 3 ) ) [top:Min_Stack:private] => 5 )