PHP 获取数组随意下标key的上一个prev和下一个next下标值

<?php $xoops[1] = &#39;小&#39;;$xoops[2] = &#39;孩&#39;;$xoops[3] = &#39;子&#39;;$xoops[4] = &#39;气&#39;;$steps = new Steps();foreach($xoops as $key=>$value){$steps->add($key);}$steps->setCurrent(3);//参数为key值echo '上一个下标：'.$steps->getPrev()."<br>";echo '指定的下标：'.$steps->getCurrent()."<br>";echo '下一个下标：'.$steps->getNext()."<br>";class Steps {     private $all;    private $count;    private $curr;     function __construct() {        $this->count = 0;    }    function add($step) {        $this->count++;        $this->all[$this->count] = $step;    }    function setCurrent($step) {        reset($this->all);        for ($i = 1; $i count; $i++) {            if ($this->all[$i] == $step)                break;            next($this->all);        }        $this->curr = current($this->all);    }    function getCurrent() {        return $this->curr;    }    function getNext() {        self::setCurrent($this->curr);        return next($this->all);    }    function getPrev() {        self::setCurrent($this->curr);        return prev($this->all);    }}

上一个下标：2指定的下标：3下一个下标：4