Runs \curl_multi_exec() inside the event loop, to prevent busy looping
private function tickInQueue() : void { if (\curl_multi_exec($this->_mh, $this->active) === \CURLM_CALL_MULTI_PERFORM) { \curl_multi_select($this->_mh, 0); P\Utils::queue()->add(Closure::fromCallable([ $this, 'tickInQueue', ])); } }