php代码执行时间

<?php
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);
}
}

$runtime= new runtime;
$runtime->start();

/*****你的代码开始********/
$a = 0;
for($i=0; $i<1000000; $i++){
$a += $i;
}
/*****你的代码结束*******/

$runtime->stop();
echo "页面执行时间: ".$runtime->spent()." 毫秒";
?>