PHP code running time view class code sharing

The code is as follows:
//date:2011-08-05
class RunTime//Page execution time class
{
private $starttime;//Page start execution time
private $stoptime;//Page end execution time
private $ spendtime;//The time it takes to execute the page
function getmicrotime()//Get the floating point number that returns the current microsecond
{
list($usec,$sec)=explode(" ",microtime());
return ((( float)$usec + (float)$sec);
}
function start()//The page starts executing the function and returns the time when the page starts executing
{
$this->starttime=$this->getmicrotime() ;
}
function end()//Display the page execution time
{
$this->stoptime=$this->getmicrotime();
$this->spendtime=$this->stoptime-$ this->starttime;
//return round($this->spendtime,10);
}
function display()
{
//$this->end();
echo "

Running time: ".round($this->spendtime,10)."Seconds

";
}
}
/*Call method
$timer=new Runtime();
$timer-> start();