public function insertVerifier($eventName, callable $verifier)
    {
        $this->attachListener($eventName, function (EventInterface $event) use ($verifier) {
            $result = $verifier($event);

            //return type hints pls
            if ($result instanceof ResultInterface) {
                $this->resultAggregator->add($result);
            } else {
                //??!!
            }
        });
    }
public function insertVerifier($eventName, callable $verifier)
    {
        $this->attachListener($eventName, function (EventInterface $event) use ($verifier) {
            $result = $verifier($event);

            //return type hints pls
            if ($result instanceof ResultInterface) {
                $this->resultAggregator->add($result);
            } else {
                //??!!
            }
        });
    }
public function insertVerifier ( $ eventName , callable $ verifier ) { $ this -> attachListener ( $ eventName , function ( EventInterface $ event ) use ( $ verifier ) { $ result = $ verifier ( $ event ) ; //return type hints pls if ( $ result instanceof ResultInterface ) { $ this -> resultAggregator -> add ( $ result ) ; } else { //??!! } } ) ; }
Insert a verifier callback which will execute at the given event name much like normal listeners.
A verifier should return an object which implements `PhpSchool\PhpWorkshop\Result\FailureInterface`
or `PhpSchool\PhpWorkshop\Result\SuccessInterface`. This result object will be added to the result aggregator.

@param string|array $eventName
@param callable $verifier
Insert a verifier callback which will execute at the given event name much like normal listeners . A verifier should return an object which implements PhpSchool \ PhpWorkshop \ Result \ FailureInterface or PhpSchool \ PhpWorkshop \ Result \ SuccessInterface . This result object will be added to the result aggregator .