I don't use Expression web but I might be able to get your started in the right direction.
It's a little confusing because you say your server is using cPanel which implies a hosting company, but then you say you are installing PHP which implies a local server. Most hosting companies have PHP ready to go.
Even though this article says it's for Dreamweaver, you can learn how to setup a testing environment and ignore the Dreamweaver step:
You might also benefit from this article:
10 Tips for getting quick help from a support forum