How to deal with Polish Characters while using regex?

\p{L} catches not only Polish letters, but also Russian for example, may be some other too.

If you, like me, need Polish letters only, take this:

[AaĄąBbCcĆćDdEeĘęFfGgHhIiJjKkLlŁłMmNnŃńOoÓóPpRrSsŚśTtUuWwYyZzŹźŻż]

Characters got from wiki

Use /^[\s\p{L}]+$/u (PHP syntax).

Edit: Adjusted regex to better handle whitespace.