Simple events in php

Simple class and small thought about how does events work.

<?php

interface IEventType {
    public function getType(): ?string;
}

class TestEventType implements IEventType {
    private $type = "test";

    public function getType(): ?string {
        return $this->type;
    }
}

class Event {
    private $function;
    private $eventType;

    public function fire(array $args) {
        return call_user_func_array($this->function, $args);
    }

    public function getFunction(): ?callable {
        return $this->function();
    }

    public function setFunction(callable $function): self {
        $this->function = $function;
        return $this;
    }

    public function getEventType(): ?IEventType {
        return $this->eventType;
    }

    public function setEventType(IEventType $eventType): self {
        $this->eventType = $eventType;
        return $this;
    }
}

class EventSubscriber {
    private $events;

    public function addEvent(Event $event): self {
        $this->events[] = $event;
        return $this;
    }

    public function removeEvent(Event $event): self {
        foreach ($this->events as $eventC) {
            if ($eventC === $event) {
                unset ($eventC);
            }
        }
        return $this;
    }

    public function fireEvents(IEventType $eventType): array {
        $result = [];

        foreach ($this->events as $event) {
            if ($event->getEventType() === $eventType) {
                $result[] = $event->fire([]);
            }
        }

        return $result;
    }
}

$testEventType = new TestEventType();
$event = new Event();
$event->setEventType($testEventType);
$event->setFunction(function () {
    echo 55;
    return 22;
});
$eventSubscriber = new EventSubscriber();
$eventSubscriber->addEvent($event);
$res = $eventSubscriber->fireEvents($testEventType);
var_dump($res);