code: public function notify() {
  			declare(ticks=1);
  			if (is_array($this->_caller) && !empty($this->_caller)) {
  				// array
  				return call_user_func_array($this->_caller, [$this->_interrupt]);
  			} else if ($this->_caller instanceof Closure) {
  				// closure
  				return $this->_caller->call($this, $this->_interrupt);
  			} else if (is_callable($this->_caller)) {
  				// callable
  				$cl = Closure::fromCallable($this->_caller);
  				return $cl->call($this,$this->_interrupt);
  			}
  			return null;
  		}
docs: Called on interruption
  @return null|int