PHP manual [http://www.php.net/manual/en/language.oop5.basic.php] gives a valid class name as:

     ^[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*$

I can't see an equivalent official regex for namespaces.

Is this equivalent to what you have, or are there some extra allowed characters?