private static function update_lessons( $lessons, $section ) {

		$ret = array();

		foreach ( $lessons as $lesson_data ) {

			if ( ! isset( $lesson_data['id'] ) ) {
				continue;
			}

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

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

				$lesson = new LLMS_Lesson(
					'new',
					array(
						'post_title' => isset( $lesson_data['title'] ) ? $lesson_data['title'] : __( 'New Lesson', 'lifterlms' ),
					)
				);

				$created = true;

			} else {

				$lesson  = llms_get_post( $lesson_data['id'] );
				$created = false;

			}

			if ( empty( $lesson ) || ! is_a( $lesson, 'LLMS_Lesson' ) ) {

				// Translators: %s = Lesson post id.
				$res['error'] = sprintf( esc_html__( 'Unable to update lesson "%s". Invalid lesson ID.', 'lifterlms' ), $lesson_data['id'] );

			} else {

				/**
				 * If the parent section was just created the lesson will have a temp id
				 * replace it with the newly created section's real ID.
				 */
				if ( ! isset( $lesson_data['parent_section'] ) || self::is_temp_id( $lesson_data['parent_section'] ) ) {
					$lesson_data['parent_section'] = $section->get( 'id' );
				}

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

				$properties = array_merge(
					array_keys( $lesson->get_properties() ),
					array(
						'content',
						'title',
					)
				);

				$skip_props = apply_filters( 'llms_builder_update_lesson_skip_props', array( 'quiz' ) );

				// Update all updatable properties.
				foreach ( $properties as $prop ) {
					if ( isset( $lesson_data[ $prop ] ) && ! in_array( $prop, $skip_props, true ) ) {
						$lesson->set( $prop, $lesson_data[ $prop ] );
					}
				}

				// Update all custom fields.
				self::update_custom_schemas( 'lesson', $lesson, $lesson_data );

				// During clone's we want to ensure custom field data comes with the lesson.
				if ( $created && isset( $lesson_data['custom'] ) ) {
					foreach ( $lesson_data['custom'] as $custom_key => $custom_vals ) {
						foreach ( $custom_vals as $val ) {
							add_post_meta( $lesson->get( 'id' ), $custom_key, maybe_unserialize( $val ) );
						}
					}
				}

				// Ensure slug gets updated when changing title from default "New Lesson".
				if ( isset( $lesson_data['title'] ) && ! $lesson->has_modified_slug() ) {
					$lesson->set( 'name', sanitize_title( $lesson_data['title'] ) );
				}

				if ( ! empty( $lesson_data['quiz'] ) && is_array( $lesson_data['quiz'] ) ) {
					$res['quiz'] = self::update_quiz( $lesson_data['quiz'], $lesson );
				}
			}

			// Allow 3rd parties to update custom data.
			$res = apply_filters( 'llms_builder_update_lesson', $res, $lesson_data, $lesson, $created );

			array_push( $ret, $res );

		}

		return $ret;

	}