如何用php实现栈结构

<?php
class HeapStack{
    private $stackArr = array();
    private $stackMaxTop = 10; // 栈顶最大值(用于控制栈长度，是否栈满)
    private $top = -1; // 栈顶（会随着push或pop的操作而变化）
    private $out;

    /**
     * 入栈
     *
     */
    public function pushValue($value='')
    {
        if(empty($value))
            return '压入的值不能为空';

        if($this->top == $this->stackMaxTop)
            return '栈内已满';
        array_push($this->stackArr, $value);
        ++$this->top;
        return '入栈成功，栈顶值：'.$this->top;
    }

    /**
     * 出栈
     *
     */
    public function popValue()
    {
        if($this->top == -1)
            return '栈内没有数据';

        $this->out = array_pop($this->stackArr);
        --$this->top;
        return '出栈成功，当前栈顶值:'.$this->top.'出栈值：'.$this->out;
    }

    /**
     * 获取栈内信息
     */
    public function getSatck()
    {
        return $this->stackArr;
    }

    public function __destruct()
    {
        echo 'over ';
    }
}

$stack = new HeapStack();
echo $stack->pushValue('stackValue')."\n";
echo $stack->pushValue('stackValue2')."\n";
var_dump($stack->getSatck());
echo $stack->popValue()."\n";
var_dump($stack->getSatck());