bp_notifications_get_notifications_for_user( int $user_id, string $format = 'string' )

function bp_notifications_get_notifications_for_user( $user_id, $format = 'string' ) {
	$bp = buddypress();

	$notifications = bp_notifications_get_grouped_notifications_for_user( $user_id );

	// Calculate a renderable output for each notification type.
	foreach ( $notifications as $notification_item ) {

		$component_name = $notification_item->component_name;
		// We prefer that extended profile component-related notifications use
		// the component_name of 'xprofile'. However, the extended profile child
		// object in the $bp object is keyed as 'profile', which is where we need
		// to look for the registered notification callback.
		if ( 'xprofile' == $notification_item->component_name ) {
			$component_name = 'profile';
		}

		// Callback function exists.
		if ( isset( $bp->{$component_name}->notification_callback ) && is_callable( $bp->{$component_name}->notification_callback ) ) {

			// Function should return an object.
			if ( 'object' === $format ) {

				// Retrieve the content of the notification using the callback.
				$content = call_user_func( $bp->{$component_name}->notification_callback, $notification_item->component_action, $notification_item->item_id, $notification_item->secondary_item_id, $notification_item->total_count, 'array', $notification_item->id );

				// Create the object to be returned.
				$notification_object = $notification_item;

				// Minimal backpat with non-compatible notification
				// callback functions.
				if ( is_string( $content ) ) {
					$notification_object->content = $content;
					$notification_object->href    = bp_loggedin_user_domain();
				} else {
					$notification_object->content = $content['text'];
					$notification_object->href    = $content['link'];
				}

				$renderable[] = $notification_object;

				// Return an array of content strings.
			} else {
				$content      = call_user_func( $bp->{$component_name}->notification_callback, $notification_item->component_action, $notification_item->item_id, $notification_item->secondary_item_id, $notification_item->total_count, 'string', $notification_item->id );
				$renderable[] = $content;
			}

			// @deprecated format_notification_function - 1.5
		} elseif ( isset( $bp->{$component_name}->format_notification_function ) && function_exists( $bp->{$component_name}->format_notification_function ) ) {
			$renderable[] = call_user_func( $bp->{$component_name}->notification_callback, $notification_item->component_action, $notification_item->item_id, $notification_item->secondary_item_id, $notification_item->total_count );

			// Allow non BuddyPress components to hook in.
		} else {

			// The array to reference with apply_filters_ref_array().
			$ref_array = array(
				$notification_item->component_action,
				$notification_item->item_id,
				$notification_item->secondary_item_id,
				$notification_item->total_count,
				$format,
				$notification_item->component_action, // Duplicated so plugins can check the canonical action name.
				$component_name,
				$notification_item->id,
			);

			// Function should return an object.
			if ( 'object' === $format ) {

				/**
				 * Filters the notification content for notifications created by plugins.
				 * If your plugin extends the {@link BP_Component} class, you should use the
				 * 'notification_callback' parameter in your extended
				 * {@link BP_Component::setup_globals()} method instead.
				 *
				 * @since BuddyPress 1.9.0
				 * @since BuddyPress 2.6.0 Added $component_action_name, $component_name, $id as parameters.
				 *
				 * @param string $content               Component action. Deprecated. Do not do checks against this! Use
				 *                                      the 6th parameter instead - $component_action_name.
				 * @param int    $item_id               Notification item ID.
				 * @param int    $secondary_item_id     Notification secondary item ID.
				 * @param int    $action_item_count     Number of notifications with the same action.
				 * @param string $format                Format of return. Either 'string' or 'object'.
				 * @param string $component_action_name Canonical notification action.
				 * @param string $component_name        Notification component ID.
				 * @param int    $id                    Notification ID.
				 *
				 * @return string|array If $format is 'string', return a string of the notification content.
				 *                      If $format is 'object', return an array formatted like:
				 *                      array( 'text' => 'CONTENT', 'link' => 'LINK' )
				 */
				$content = apply_filters_ref_array( 'bp_notifications_get_notifications_for_user', $ref_array );

				// Create the object to be returned.
				$notification_object = $notification_item;

				// Minimal backpat with non-compatible notification
				// callback functions.
				if ( is_string( $content ) ) {
					$notification_object->content = $content;
					$notification_object->href    = bp_loggedin_user_domain();
				} else {
					$notification_object->content = $content['text'];
					$notification_object->href    = $content['link'];
				}

				$renderable[] = $notification_object;

				// Return an array of content strings.
			} else {

				/** This filters is documented in bp-notifications/bp-notifications-functions.php */
				$renderable[] = apply_filters_ref_array( 'bp_notifications_get_notifications_for_user', $ref_array );
			}
		}
	}

	// If renderable is empty array, set to false.
	if ( empty( $renderable ) ) {
		$renderable = false;
	}

	/**
	 * Filters the final array of notifications to be displayed for a user.
	 *
	 * @since BuddyPress 1.6.0
	 *
	 * @param array|bool $renderable Array of notifications to render or false if no notifications.
	 * @param int        $user_id    ID of the user whose notifications are being displayed.
	 * @param string     $format     Display format requested for the notifications.
	 */
	return apply_filters( 'bp_core_get_notifications_for_user', $renderable, $user_id, $format );
}