Simple "StopWatch" class to measure PHP execution time. The class can handle multiple separate timers at the same time

stopwatch.php

<?php
class StopWatch {
	/**
	* @var $startTimes array The start times of the StopWatches
	*/
	private static $startTimes = array();

	/**
	* Start the timer
	*
	* @param $timerName string The name of the timer
	* @return void
	*/
	public static function start($timerName = 'default') {
		self::$startTimes[$timerName] = microtime(true);
	}

	/**
	* Get the elapsed time in seconds
	*
	* @param $timerName string The name of the timer to start
	* @return float The elapsed time since start() was called
	*/
	public static function elapsed($timerName = 'default') {
		return microtime(true) - self::$startTimes[$timerName];
	}
}

// start the timer
StopWatch::start();

// your script - this is an example
sleep(2);

// check how long 2 seconds is...
echo 'Elapsed time: ' . StopWatch::elapsed() . ' seconds';

how can i start using a button and stop using also a button please help!