public function filter_response_fields( $data, $resource, $fields ) {

		if ( ! is_array( $data ) || empty( $fields ) ) {
			return $data;
		}

		$fields = explode( ',', $fields );
		$sub_fields = array();

		// get sub fields
		foreach ( $fields as $field ) {

			if ( false !== strpos( $field, '.' ) ) {

				list( $name, $value ) = explode( '.', $field );

				$sub_fields[ $name ] = $value;
			}
		}

		// iterate through top-level fields
		foreach ( $data as $data_field => $data_value ) {

			// if a field has sub-fields and the top-level field has sub-fields to filter
			if ( is_array( $data_value ) && in_array( $data_field, array_keys( $sub_fields ) ) ) {

				// iterate through each sub-field
				foreach ( $data_value as $sub_field => $sub_field_value ) {

					// remove non-matching sub-fields
					if ( ! in_array( $sub_field, $sub_fields ) ) {
						unset( $data[ $data_field ][ $sub_field ] );
					}
				}
			} else {

				// remove non-matching top-level fields
				if ( ! in_array( $data_field, $fields ) ) {
					unset( $data[ $data_field ] );
				}
			}
		}

		return $data;
	}