If you do not use Operating System related stuff ,I do not thing you will have a problem as php is one for all.
Maybe someone with more experience may say for sure .
I made a php site at resin (Java server that support php) and the only problem were the set of character encoding.
My resin server configuration wanted unicode for my language characters.
Also I made php scripts at windows with Abyss web server and then I upload them at apache and I did not had any problem.
For oracle and php I found this .
Hopefully you will be using the same Apache/PHP versions in both your environments.
Things to be careful of :
1) Using $_SERVER variables, they change per OS.
2) Case sensitivity, Windoze doesn't care, Linux DOES (and rightly so).
PHP has built in support for Oracle I believe, either through ODBC or through PHP native built in functions ( i think ). See http://uk2.php.net/oci8
Just to add to this post, i was doing some work in a Windbloze environment earlier today and ended up banging my head on the desk because .htaccess in XAMPP was making my life hell, whereas the same .htaccess in Linux was pleasantly working as expected. It all ended up being a rewrite URL, windbloze was taking /login to mean /Login and outputting the contents of a directory instead of URL rewriting as we expected to utilise the index.php file and relevant bootloader.