WP_Object_Cache::is_valid_key( int|string $key )

	protected function is_valid_key( $key ) {
		if ( is_int( $key ) ) {
			return true;
		}

		if ( is_string( $key ) && trim( $key ) !== '' ) {
			return true;
		}

		$type = gettype( $key );

		if ( ! function_exists( '__' ) ) {
			wp_load_translations_early();
		}

		$message = is_string( $key )
			? __( 'Cache key must not be an empty string.' )
			/* translators: %s: The type of the given cache key. */
			: sprintf( __( 'Cache key must be integer or non-empty string, %s given.' ), $type );

		_doing_it_wrong(
			sprintf( '%s::%s', __CLASS__, debug_backtrace( DEBUG_BACKTRACE_IGNORE_ARGS, 2 )[1]['function'] ),
			$message,
			'6.1.0'
		);

		return false;
	}