Which Version Of Php Is Best?

Had this in another thread but it's more appropriate here.

I am using a few versions of cs-cart on my server. V2.1.4, 2.2.3, 2.2.4, and 3.0.6. I'm currently on PHP Version 5.2.13.

I want to start upgrading the stores to the new version V4, and first step would be to upgrade PHP. Given these different versions of cs-cart, could I just have my hosting company upgrade php?

Would I need to modify anything once it's done to ensure the stores still work fine? I won't be able to upgrade all my stores in a single day or two, so I need to make sure that they all will work after php is upgraded.

And lastly, I see different versions php being used. Is there a specific version number that I should have my hosting company use for the php upgrade?


Already Answered. Disregard.