*/ protected $listeners = []; /** * Subscribe to an event. * * @return void */ public function on(string $eventName, callable $callBack, int $priority = 100) { if (!isset($this->listeners[$eventName])) { $this->listeners[$eventName] = [ true, // If there's only one item, it's sorted [$priority], [$callBack], ]; } else { $this->listeners[$eventName][0] = false; // marked as unsorted $this->listeners[$eventName][1][] = $priority; $this->listeners[$eventName][2][] = $callBack; } } /** * Emits an event. * * This method will return true if 0 or more listeners were successfully * handled. false is returned if one of the events broke the event chain. * * If the continueCallBack is specified, this callback will be called every * time before the next event handler is called. * * If the continueCallback returns false, event propagation stops. This * allows you to use the eventEmitter as a means for listeners to implement * functionality in your application, and break the event loop as soon as * some condition is fulfilled. * * Note that returning false from an event subscriber breaks propagation * and returns false, but if the continue-callback stops propagation, this * is still considered a 'successful' operation and returns true. * * Lastly, if there are 5 event handlers for an event. The continueCallback * will be called at most 4 times. * * @param list $arguments */ public function emit( string $eventName, array $arguments = [], ?callable $continueCallBack = null ) : bool { if ($continueCallBack === null) { foreach ($this->listeners($eventName) as $listener) { /** @psalm-suppress MixedAssignment */ $result = \call_user_func_array($listener, $arguments); if ($result === false) { return false; } } } else { $listeners = $this->listeners($eventName); $counter = \count($listeners); foreach ($listeners as $listener) { --$counter; /** @psalm-suppress MixedAssignment */ $result = \call_user_func_array($listener, $arguments); if ($result === false) { return false; } if ($counter > 0) { if (!$continueCallBack()) { break; } } } } return true; } /** * Returns the list of listeners for an event. * * The list is returned as an array, and the list of events are sorted by * their priority. * * @return callable[] */ public function listeners(string $eventName) : array { if (!isset($this->listeners[$eventName])) { return []; } // The list is not sorted if (!$this->listeners[$eventName][0]) { // Sorting \array_multisort($this->listeners[$eventName][1], SORT_NUMERIC, $this->listeners[$eventName][2]); // Marking the listeners as sorted $this->listeners[$eventName][0] = true; } return $this->listeners[$eventName][2]; } /** * Removes a specific listener from an event. * * If the listener could not be found, this method will return false. If it * was removed it will return true. */ public function removeListener(string $eventName, callable $listener) : bool { if (!isset($this->listeners[$eventName])) { return false; } foreach ($this->listeners[$eventName][2] as $index => $check) { if ($check === $listener) { unset($this->listeners[$eventName][1][$index], $this->listeners[$eventName][2][$index]); return true; } } return false; } }