private static function update_section( $section_data, $course_id ) {

		$res = array_merge(
			$section_data,
			array(
				'orig_id' => $section_data['id'],
			)
		);

		// Create a new section.
		if ( self::is_temp_id( $section_data['id'] ) ) {

			$section = new LLMS_Section( 'new' );
			$section->set( 'parent_course', $course_id );

			// Update existing section.
		} else {

			$section = llms_get_post( $section_data['id'] );

		}

		// We don't have a proper section to work with...
		if ( empty( $section ) || ! is_a( $section, 'LLMS_Section' ) ) {
			// Translators: %s = Section post id.
			$res['error'] = sprintf( esc_html__( 'Unable to update section "%s". Invalid section ID.', 'lifterlms' ), $section_data['id'] );
		} else {

			// Return the real ID (important when creating a new section).
			$res['id'] = $section->get( 'id' );

			// Run through all possible updated fields.
			foreach ( array( 'order', 'title' ) as $key ) {

				// Update those that were sent through.
				if ( isset( $section_data[ $key ] ) ) {

					$section->set( $key, $section_data[ $key ] );

				}
			}

			if ( isset( $section_data['lessons'] ) && is_array( $section_data['lessons'] ) ) {

				$res['lessons'] = self::update_lessons( $section_data['lessons'], $section );

			}
		}

		return $res;

	}