private static function stringifyKey($key): string
    {
        if ($key === null || is_scalar($key)) {
            return (string) $key;
        }

        if (is_object($key)) {
            return spl_object_hash($key);
        }

        return static::stringifyArrayKey($key);
    }
private static function stringifyKey($key): string
    {
        if ($key === null || is_scalar($key)) {
            return (string) $key;
        }

        if (is_object($key)) {
            return spl_object_hash($key);
        }

        return static::stringifyArrayKey($key);
    }
private static function stringifyKey ( $ key ) : string { if ( $ key === null || is_scalar ( $ key ) ) { return ( string ) $ key ; } if ( is_object ( $ key ) ) { return spl_object_hash ( $ key ) ; } return static :: stringifyArrayKey ( $ key ) ; }
Calculates string representing specified key

@param mixed $key
@return string
Calculates string representing specified key