faking method overloading

file.php

<?php
// method overloading example (not possible in php)
final class SomeEventListener {
    public function when(EmployeeWasHired $event) {
        // set a salary
    }

    public function when(EmployeeWasPromoted $event) {
        // increase salary
    }
}

// Faking method overloading. Noisy but good enough.
final class SomeEventListener {
    public function when(Event $event) {
        switch (true) {
            case $event instanceof EmployeeWasHired:
                return $this->whenEmployeeWasHired($event);
            case $event instanceof EmployeeWasPromoted:
                return $this->whenEmployeeWasPromoted($event);
        }
    }

    public function whenEmployeeWasHired(EmployeeWasHired $event) {
        // set a salary
    }

    public function whenEmployeeWasPromoted(EmployeeWasPromoted $event) {
        // increase salary
    }
}

I really don't like switches used in this way - I think it makes method extraction a little harder to do. In this case, I'd prefer:

public function when(Event $event) {
    // switch (true) {
    //     case $event instanceof EmployeeWasHired:
    //         return $this->whenEmployeeWasHired($event);
    //     case $event instanceof EmployeeWasPromoted:
    //         return $this->whenEmployeeWasPromoted($event);
    // }

    if ($event instanceof EmployeeWasHired) {
        return $this->whenEmployeeWasHired($event);
    }

    if ($event instanceof EmployeeWasPromoted) {
        return $this->whenEmployeeWasPromoted($event);
    }

    throw new InvalidArgumentException("not implemented");
}

...but I agree with what you're saying in the thread! :)

I also like a more generic approach

<?php

class Test {

    public function on(Event $event) {
        $eventName = (new ReflectionClass($event))->getShortName();
        $methodName = 'on' . $eventName;
        $callable = [$this, $methodName];
        if ( !is_callable($callable) ) {
            throw ListenerMethodNotImplemented::forEvent($event); // or early return
        }
        call_user_func($callable, $event);
    }

    protected function onEmployeeHired(EmployeeHired $event) {
        // ...
    }

}