PHP数据结构之实现栈

接着前面PHP数据结构来学习，今天写的是实现栈。

<?php
	class stack                      //定义一个栈的类
	{
		private $size;               //栈的空间大小
		private $top;                // 栈的指针
		private $stack_arr;          //栈的空间

		public function __construct($size)    //初始化一个空栈
		{
			$this->top=-1;
			$this->size=$size;
			$this->stack_arr=array();
		}
		public function push($data)           //入栈操作，先判断栈是否已满
		{
			if($this->top==$this->size-1)
				echo "The stack is full";
			else
				$this->stack_arr[++$this->top]=$data;
		}
		public function pop()               //出栈，取栈顶元素，先判断是否为空栈
		{
			if($this->top==-1)
				echo "The stack is empty";
			else
				return $this->stack_arr[$this->top--];
		}

		public function getlength()          //获取栈的大小
		{
			return $this->top+1;
		}

		public function print_stack()        //输出栈内元素
		{
			$tem=$this->top;
			while($tem!=-1)
			{
				echo $this->stack_arr[$tem--];
			}
		}
	}

	$stack=new stack(3);
	$stack->push('a');
	$stack->push('b');
	$stack->push('c');
	echo $stack->getlength();
	echo "<br/>";
	$stack->print_stack();
	echo "<br/>";
	echo $stack->pop();
	echo "<br/>";
	$stack->push('d');
	$stack->print_stack();

?>

　　运行结果截图如下：