转载链接：http://blog.csdn.net/php_boy/article/details/6450678

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";