function dozent_get_next_previous_content_id( $content_ID = 0 ) {
		$content_ID = dozent_get_post_id( $content_ID );

		$course_id       = dozent_get_course_id_by_content( $content_ID );
		$course_contents = dozent_get_course_contents( $course_id );

		$previous_id = 0;
		$next_id     = 0;

		if ( dozent_count( $course_contents ) ) {
			$ids = wp_list_pluck( $course_contents, 'ID' );

			$i = 0;
			foreach ( $ids as $key => $id ) {
				$previous_i = $key - 1;
				$next_i     = $key + 1;

				if ( $id == $content_ID ) {
					if ( isset( $ids[ $previous_i ] ) ) {
						$previous_id = $ids[ $previous_i ];
					}
					if ( isset( $ids[ $next_i ] ) ) {
						$next_id = $ids[ $next_i ];
					}

					break;
				}
				$i ++;
			}
		}

		return (object) [ 'previous_id' => $previous_id, 'next_id' => $next_id ];
	}