src/properties/class-papi-property-user.php
public function format_value( $value, $slug, $post_id ) {
		if ( is_object( $value ) && isset( $value->ID ) ) {
			$value = $value->ID;
		}

		if ( is_numeric( $value ) ) {
			return $value === 0 ? null : new WP_User( $value );
		}

		return $value;
	}
public function format_value( $value, $slug, $post_id ) {
		if ( is_object( $value ) && isset( $value->ID ) ) {
			$value = $value->ID;
		}

		if ( is_numeric( $value ) ) {
			return $value === 0 ? null : new WP_User( $value );
		}

		return $value;
	}
Format the value of the property before it's returned
to WordPress admin or the site.

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

@return null|WP_User