$pagestartime=microtime();
?>

网页内容
...
...

$pageendtime = microtime();
$starttime = explode(" ",$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";
?>