PHP 计算页面执行时间

< ?php class runtime {      var $StartTime = 0;      var $StopTime = 0;        function get_microtime()      {          list($usec, $sec) = explode(' ', microtime());          return ((float)$usec + (float)$sec);      }        function start()      {          $this->StartTime = $this->get_microtime();      }        function stop()      {          $this->StopTime = $this->get_microtime();      }        function spent()      {          return round(($this->StopTime - $this->StartTime) * 1000, 1);      }    }     //例子  $runtime= new runtime; $runtime->start();   //你的代码开始   $a = 0; for($i=0; $i<1000000; $i++) {     $a += $i; }   //你的代码结束   $runtime->stop(); echo "页面执行时间: ".$runtime->spent()." 毫秒";   ?>