src/Timer.php
public static function start(string $key = 'default'): void {
    if (isset(self::$timers[$key])) {
      self::$timers[$key]->start();
    }
    else {
      self::$timers[$key] = new Stopwatch();
    }
  }
public static function start(string $key = 'default'): void {
    if (isset(self::$timers[$key])) {
      self::$timers[$key]->start();
    }
    else {
      self::$timers[$key] = new Stopwatch();
    }
  }
Start or resume the timer.

Call this method to start the timer with a given key. The default key
is "default", and used in @see \Ayesh\PHP_Timer\Timer::read() and reset()
methods as well

Calling this with the same $key will not restart the timer if it has already
started.

@param string $key