统计php程序运行时间

<?php
  $pagestartime=microtime();
?>
<?php 程序段?>
<?php
  $pageendtime = microtime();
  echo $pageendtime."<br/>";
  $starttime = explode(" ",$pagestartime);
  $endtime = explode(" ",$pageendtime);
  $totaltime = $endtime[0]-$starttime[0]+$endtime[1]-$starttime[1];
  $timecost = sprintf("%s",$totaltime);
  echo "页面运行时间: $timecost 秒";
?>