public static function isAbsolutePath($path) : bool
    {
        /*
         * This is definitive if true but fails if $path does not exist or contains
         * a symbolic link.
         */
        if (realpath($path) == $path) {
            return true;
        }

        if (strlen($path) == 0 || $path[0] == '.') {
            return false;
        }

        // Windows allows absolute paths like this.
        if (preg_match('#^[a-zA-Z]:\\\\#', $path)) {
            return true;
        }

        // A path starting with / or \ is absolute; anything else is relative.
        return ( $path[0] == '/' || $path[0] == '\\' );
    }