class  c_Timer  {
    var  $t_start  =  0;
    var  $t_stop  =  0;
    var  $t_elapsed  =  0;
 
 
    function  start()  {  $this->t_start  =  microtime();  }
 
    function  stop()    {  $this->t_stop    =  microtime();  }
 
    function  elapsed()  {
        if  ($this->t_elapsed)  {
            return  $this->t_elapsed;
        }  else  {
            $start_u  =  substr($this->t_start,0,10);
            $start_s  =  substr($this->t_start,11,10);
            $stop_u    =  substr($this->t_stop,0,10);
            $stop_s    =  substr($this->t_stop,11,10);
            $start_total  =  doubleval($start_u)  +  $start_s;
            $stop_total    =  doubleval($stop_u)  +  $stop_s;
 
            $this->t_elapsed  =  $stop_total  -  $start_total;
 
            return  $this->t_elapsed;
        }
    }
};
 
//  Here's  an  example  usage:
 
        $timer  =  new  c_Timer;
 
        $timer->start();
        echo  "<hr>";
      //这里执行的代码


        $timer->stop();
 
        echo  $timer->elapsed();