Submission::sync_upstream()

	public function sync_upstream() {
		$result = parent::sync_upstream();

		if ( is_wp_error( $result ) ) {
			return $result;
		}

		if ( null !== $this->values ) {
			$manager = $this->manager->get_child_manager( 'submission_values' );

			$ids = array();
			foreach ( $this->values as $item ) {
				$submission_value = null;
				if ( ! empty( $item['id'] ) ) {
					$submission_value = $manager->get( $item['id'] );
					if ( $submission_value && $this->id !== $submission_value->submission_id ) {
						continue;
					}
				}

				if ( ! $submission_value ) {
					$submission_value = $manager->create();
				}

				$submission_value->submission_id = $this->id;
				$submission_value->field         = $item['field'];
				$submission_value->value         = $item['value'];
				if ( ! empty( $item['element_id'] ) ) {
					$submission_value->element_id = $item['element_id'];
				}

				$submission_value->sync_upstream();

				if ( empty( $submission_value->id ) ) {
					continue;
				}

				$ids[] = $submission_value->id;
			}

			if ( ! empty( $ids ) ) {
				$old_values = $this->get_submission_values( array(
					'exclude' => $ids,
				) );
				foreach ( $old_values as $old_value ) {
					$old_value->delete();
				}
			}

			$this->values = null;
		}

		return $result;
	}