Twig Filter to measure execution time

TwigTimer.php

<?php

namespace MyApp\Helpers;

class TwigTimer extends \Twig_Extension {

	  protected $total_time = array();
    protected $previous_time = array();

    /**
     * Returns the canonical name of this helper.
     *
     * @return string The canonical name
     */
    public function getName()
    {
        return 'twigtimer';
    }
    
    /**
     * Returns a list of twig functions.
     *
     * @return array An array
     */
    public function getFunctions()
    {
        $names = array(
            'start_timer'     => 'startTimer',
            'stop_timer'      => 'stopTimer',
            'get_timer_total' => 'getTimerTotal',
        );
        $funcs = array();
        foreach ($names as $twig => $local) {
            $funcs[$twig] = new \Twig_Function_Method($this, $local, array('is_safe' => array('html')));
        }
        return $funcs;
    }

	/**
     * do Start Timer Filter
     *
     * @return boolean
     */
    public function startTimer($label) {
        $now = microtime(true);
 
        if (!array_key_exists($label, $this->total_time)) {
            $this->total_time[$label] = 0;
        }
 
        $this->previous_time[$label] = $now;
        return;
    }
    /**
     * do Stop Timer Filter
     *
     * @return boolean
     */
    public function stopTimer($label) {
        $now = microtime(true);
        $out = $now - $this->previous_time[$label];
        $this->total_time[$label] += $out;
        return;
    }
    /**
     * do Get Total Time
     *
     * @return boolean
     */
    public function getTimerTotal($label) {
        return $this->total_time[$label];
    }

}