On the contrary, even with this idiosyncrasy PHP is very widely used in Turkey. I struggled with these on a daily basis. It's not in my daily customs to code nowadays so I'm very happy :)
actually, we have similar issues on lots of libc dependent applications/libraries. the main issue is İi -> Iı conversions :(
Do most other languages allow you to change the language you program in or do most just force you to use english?
on most (lets say not most bu some of them) application we need to set our environment something but tr_TR. We can use our applications in Turkish but env (actually LC_CTYPE i think?) should be something other than tr_TR, afaik
That's because one of the stupidest bugs I've heard of: if you select the Turkey language (tr_TR) as locale, your PHP-code breaks:
https://bugs.php.net/bug.php?id=18556
Fortunately, it will be fixed in the upcoming PHP 5.5.