<?php
class Timer {
    private $markers;

    public function __construct() {
        $this->markers = array();
    }

    public function start() {
        $this->setMarker('Start');
    }
    
    public function stop() {
        $this->setMarker('Stop');
    }
    
    public function setMarker($name) {
        $this->markers[$name] = $this->_getMicrotime();
    }
    
    public function _getMicrotime() {
        $microtime = explode(' ', microtime());
        return $microtime[1].substr($microtime[0], 1);
    }
    
    public function timeElapsed($start = 'Start', $end = 'Stop') {
        if ($end == 'Stop' && !isset($this->markers['Stop'])) {
            $this->markers['Stop'] = $this->_getMicrotime();
        }
        
        if (extension_loaded('bcmath')) {
            return bcsub($this->markers[$end], $this->markers[$start], 6);
        } else {
            return $this->markers[$end] - $this->markers[$start];
        }
    }
    
    public function display() {
        print $this->timeElapsed();
    }
}
?>