php実行時間、メモリ消費量の表示

<?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); 
    } 

    /*         */
    function memory(){
        $size = memory_get_usage();
        $unit = array('b','kb','mb','gb','tb','pb'); 
        return @round($size/pow(1024,($i=floor(log($size,1024)))),2).' '.$unit[$i]; 
    } 
}
?>