It's interesting that Turkish is bidirectionally phonetic. That's not always the case. Some languages have strict text->speech rules but ambiguities in speech->text. Some are the other way around. I seem to recall that 'z' in Italian has some ambiguity like that, but I forget the details.
Dialects within the country and in Cyprus use the "Istanbul" Turkish for formal communication, so there exists only one "correct" way to spell each word. But of course, for casual talk and texting, each dialect writes certain words the way they pronounce them.
\* One cool corollary of the WYRIWYP rule is that there's only one correct spelling of any given sequence of sounds. If you take some native Turkish speakers and have them listen to a made-up word, 99% of them will come up with the same spelling independently of each other.