php 计算代码执行时间

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);
    }
}


$run_time = new runtime();
$run_time->start();
//begin your code
//end your code
$run_time->stop();
echo "Script running time:".$run_time->spent()."ms";