WordImpress / Give

	 *

	 * @return mixed|null|string

	 */

	public function get_user_public_key( $user_id = 0 ) {

		global $wpdb;

		if ( empty( $user_id ) ) {

			return '';

		}

		$cache_key       = md5( 'give_api_user_public_key' . $user_id );

		$user_public_key = Give_Cache::get( $cache_key, true );

		if ( empty( $user_public_key ) ) {

			$user_public_key = $wpdb->get_var( $wpdb->prepare( "SELECT meta_key FROM $wpdb->usermeta WHERE meta_value = 'give_user_public_key' AND user_id = %d", $user_id ) );

			Give_Cache::set( $cache_key, $user_public_key, HOUR_IN_SECONDS, true );

		}

		return $user_public_key;

	}

	/**

	 * Get user secret key.

	 *

	 * @return mixed|null|string

	 */

	public function get_user_secret_key( $user_id = 0 ) {

		global $wpdb;

		if ( empty( $user_id ) ) {

			return '';

		}

		$cache_key       = md5( 'give_api_user_secret_key' . $user_id );

		$user_secret_key = Give_Cache::get( $cache_key, true );

		if ( empty( $user_secret_key ) ) {

			$user_secret_key = $wpdb->get_var( $wpdb->prepare( "SELECT meta_key FROM $wpdb->usermeta WHERE meta_value = 'give_user_secret_key' AND user_id = %d", $user_id ) );

			Give_Cache::set( $cache_key, $user_secret_key, HOUR_IN_SECONDS, true );

		}

		return $user_secret_key;

	}

	/**

	 * Displays a missing authentication error if all the parameters are not met.