nu2php

I'm new to PHP so maybe I'm missing the obvious but the problem isn't making sense... when creating my pages in DW, if I preview the page, the temporary file uploads & is viewable... but, once I upload the actual file itself, it is a blank page. My connections are correct & the file makes it to the server & appears intact. I can view other .php files on the server so I'm guessing it is something in transit but it doesn't make sense that it works when I preview in browser. Please advise - I'm running out of hair to pull! Thanks!