Hooks::register( string $hook, callable $callback, int $priority = 0 )

37	public function register($hook, $callback, $priority = 0) {38		if (is_string($hook) === false) {39			throw InvalidArgument::create(1, '$hook', 'string', gettype($hook));40		}41 42		if (is_callable($callback) === false) {43			throw InvalidArgument::create(2, '$callback', 'callable', gettype($callback));44		}45 46		if (InputValidator::is_numeric_array_key($priority) === false) {47			throw InvalidArgument::create(3, '$priority', 'integer', gettype($priority));48		}49 50		if (!isset($this->hooks[$hook])) {51			$this->hooks[$hook] = [52				$priority => [],53			];54		} elseif (!isset($this->hooks[$hook][$priority])) {55			$this->hooks[$hook][$priority] = [];56		}57 58		$this->hooks[$hook][$priority][] = $callback;59	}