encryption for what? if you're talking about an app file, they can name them whatever they want. cod names them .iw . but essentially, they are compiled c++ files, which makes them into binary code (not readable code).
if you want to have story.php to be story.wz, you can without much effort. both involve htaccess. the first way (which i would suggest) is to add the application-add-type phpv2 .wz to htaccess (might not be the correct syntax, but it's along the lines), or use mod rewrite to make all .php to show .wz in the url bar.