测试php代码的运行时间

<?php
    class TestTime{
        private $stime;
        private $etime;
        public function __construct(){
            $this->stime = microtime(true);
        }

        public function start(){
            $this->stime = microtime(true);
        }

        public function end(){
            $this->etime = microtime(true);
            echo round(($this->etime - $this->stime) * 1000,5).‘毫秒‘;
            $this->start();
        }
    }
?>