PHP record page execution time code

<?php 
class runtime
{ 
    var $StartTime = 0; 
    var $StopTime = 0; 
    function get_microtime() 
    { 
        list($usec, $sec) = explode(&#39; &#39;, microtime()); 
        return ((float)$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); 
    } 
}
//例子 
$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";
?>