计算页面运行时间类

<?php
error_reporting(E_ALL);
class RunTime{
    private $startTime='';
    private $endTime='';
    function __construct() {
        $this->startTime = $this->getMicroTimeAsFloat();
    }
    function getMicroTimeAsFloat(){
        list($fractionalSeconds,$seconds)=explode(" ", microtime());
        return ((float)$seconds + (float)$fractionalSeconds);
    }
    function elapsed(){
        $this->endTime = $this->getMicroTimeAsFloat();
        return ($this->endTime - $this->startTime);
    }
}
运行方式：引入该类，在页面头部初始化，$rt= new Runtime();  页面底部显示 echo $rt->elapsed();