Code Changes

	/** @var array */
	protected $module_categories = array();

		$parent = $data['parent_id'] = $this->get_parent_module_id($parent, $data);

			break;

			case 'reverse':
				// Reversing a reverse is just the call itself
				$call = array_shift($arguments);

	}

	/**
	* Get the list of installed module categories
	*	key - module_id
	*	value - module_langname
	*
	* @return null
	*/
	protected function get_categories_list()
	{
		// Select the top level categories
		// and 2nd level [sub]categories
		$sql = 'SELECT m2.module_id, m2.module_langname
			FROM ' . $this->modules_table . ' m1, ' . $this->modules_table . " m2
			WHERE m1.parent_id = 0
				AND (m1.module_id = m2.module_id OR m2.parent_id = m1.module_id)
			ORDER BY m1.module_id, m2.module_id ASC";

		$result = $this->db->sql_query($sql);
		while ($row = $this->db->sql_fetchrow($result))
		{
			$this->module_categories[(int) $row['module_id']] = $row['module_langname'];
		}
		$this->db->sql_freeresult($result);
	}

	/**
	* Get parent module id
	*
	* @param string|int $parent_id The parent module_id|module_langname
	* @param int|string|array $data The module_id, module_langname for existance checking or module data array for adding
	* @param bool $throw_exception The flag indicating if exception should be thrown on error
	* @return mixed The int parent module_id or false
	* @throws \phpbb\db\migration\exception
	*/
	public function get_parent_module_id($parent_id, $data = '', $throw_exception = true)
	{
		// Initialize exception object placeholder
		$exception = false;

		// Allow '' to be sent as 0
		$parent_id = $parent_id ?: 0;

		// If automatic adding is in action, convert array back to string to simplify things
		if (is_array($data) && sizeof($data) == 1)
		{
			$data = $data['module_langname'];
		}

		if (!is_numeric($parent_id))
		{
			// Refresh the $module_categories array
			$this->get_categories_list();

			// Search for the parent module_langname
			$ids = array_keys($this->module_categories, $parent_id);

			switch (sizeof($ids))
			{
				// No parent with the given module_langname exist
				case 0:
					$exception = new \phpbb\db\migration\exception('MODULE_NOT_EXIST', $parent_id);
				break;

				// Return the module id
				case 1:
					$parent_id = (int) $ids[0];
				break;

				// Several modules with the given module_langname were found
				// Try to determine the parent_id by the neighbour module parent
				default:
					if (is_array($data) && (isset($data['before']) || isset($data['after'])))
					{
						$neighbour_module_langname = isset($data['before']) ? $data['before'] : $data['after'];
						$sql = 'SELECT parent_id
							FROM ' . $this->modules_table . "
							WHERE module_langname = '" . $this->db->sql_escape($neighbour_module_langname) . "'
								AND " . $this->db->sql_in_set('parent_id', $ids);
						$result = $this->db->sql_query($sql);
						$parent_id = (int) $this->db->sql_fetchfield('parent_id');
						if (!$parent_id)
						{
							$exception = new \phpbb\db\migration\exception('PARENT_MODULE_FIND_ERROR', $data['parent_id']);
						}
					}
					else if (!empty($data) && !is_array($data))
					{
						// The module_langname is set, checking for the module existance
						// As more than 1 parents were found already, there's no way for null parent_id here
						$sql = 'SELECT m2.module_id as module_parent_id
							FROM ' . $this->modules_table . ' m1, ' . $this->modules_table . " m2
							WHERE " . ((is_numeric($data)) ? 'm1.module_id = ' . (int) $data : "m1.module_langname = '" . $this->db->sql_escape($data)) . "'
								AND m2.module_id = m1.parent_id
								AND " . $this->db->sql_in_set('m2.module_id', $ids);
						$result = $this->db->sql_query($sql);
						$parent_id = (int) $this->db->sql_fetchfield('module_parent_id');
					}
					else
					{
						//Unable to get the parent module id, throwing an exception
						$exception = new \phpbb\db\migration\exception('MODULE_EXIST_MULTIPLE', $parent_id);
					}
				break;
			}
		}

		if ($exception !== false)
		{
			if ($throw_exception)
			{
				throw $exception;
			}
			return false;
		}

		return $parent_id;