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();