PHPを使用してスタック構造を実装する方法を教えます

<?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($value=&#39;&#39;)
    {
        if(empty($value))
            return &#39;压入的值不能为空&#39;;

        if($this->top == $this->stackMaxTop)
            return &#39;栈内已满&#39;;
        array_push($this->stackArr, $value);
        ++$this->top;
        return &#39;入栈成功，栈顶值：&#39;.$this->top;
    }

    /**
     * 出栈
     *
     */
    public function popValue()
    {
        if($this->top == -1)
            return &#39;栈内没有数据&#39;;

        $this->out = array_pop($this->stackArr);
        --$this->top;
        return &#39;出栈成功，当前栈顶值:&#39;.$this->top.&#39;出栈值：&#39;.$this->out;
    }

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

    public function __destruct()
    {
        echo &#39;over &#39;;
    }
}

$stack = new HeapStack();
echo $stack->pushValue(&#39;stackValue&#39;)."\n";
echo $stack->pushValue(&#39;stackValue2&#39;)."\n";
var_dump($stack->getSatck());
echo $stack->popValue()."\n";
var_dump($stack->getSatck());