src/properties/class-papi-property-relationship.php
public function update_value( $values, $slug, $post_id ) {
		$values = $this->format_value( $values, $slug, $post_id );
		$values = array_map( function ( $item ) {
			if ( $item instanceof WP_Post ) {
				$item = $this->convert_post_to_item( $item );
			}

			if ( isset( $item->title ) ) {
				unset( $item->title );
			}

			return $item;
		}, $values );

		return papi_maybe_json_decode( $values );
	}
public function update_value( $values, $slug, $post_id ) {
		$values = $this->format_value( $values, $slug, $post_id );
		$values = array_map( function ( $item ) {
			if ( $item instanceof WP_Post ) {
				$item = $this->convert_post_to_item( $item );
			}

			if ( isset( $item->title ) ) {
				unset( $item->title );
			}

			return $item;
		}, $values );

		return papi_maybe_json_decode( $values );
	}
Sort the values on update.

@param  mixed  $values
@param  string $slug
@param  int    $post_id

@return string