public function start()
    {
        if ($this->isProfiling) {
            return false;
        }
        $backtrace = \debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);
        $backtrace = $this->backtraceRemoveInternal($backtrace);
        foreach ($backtrace as $frame) {
            $class = isset($frame['class']) ? $frame['class'].'::' : '';
            $this->rootStack[] = $class.$frame['function'];
        }
        \register_tick_function(array($this, 'tickFunction'));
        $this->isProfiling = true;
        $this->timeLastTick = \microtime(true);
        return true;
    }