How much time you have?
If you have two weeks, I would suggest you use 5 days to read a good php book to get the basic ideas. Including set a php platform you can work with, test the simple codes in your book. I taught myself ASP in 1 week and PHP in 1 week. Anyone with a programming background can do that. By the way, you are in school and you have C background. Today's school still uses C not java or something else? I went to computer school a long time ago, we already used C++ and mostly Java then.
The books I used for ASP and PHP are
Professional ASP Programming
Professional PHP Programming
They might be too old now.
3 days to solve the problems and search the web for the sample scripts such as validation etc. (There are scripts samples for all your requests.)
2 days to refine your script and prepare to answer their questions. Plus additional knowledge you may want to get to show your future boss, such as email header injection attacks of the php email form etc.
If you have less than 2 weeks, then try to concentrate on the basic parts and the parts which has something to do with your project.
There will be scripts to cover all your requests you need the knowledge of php to merge them together.