Possible to have php v5.4 for one site and 5.3 for rest?

Whether you're "asking for a friend" or not, the answers given in this thread are still valid - the errors your friend is getting shouldn't be hard to fix - if he can't do it himself, then hire someone - because crap like that is part of the reason why we get hacked accounts, compromised servers and even more spam and crap being spewed out all over the web.
Updating code should be one of the top priorities - there are always new bugs, new holes in code being found - fixing them should be mandatory.
As for the "not being nerds" - that is perfectly fine, but then you don't really have a foot to stand on when it comes to managing servers - that's sort of the problem nowadays - since everything is very easy to get going, and pretty cheap to boot, everyone and your grandma is setting up shop - without as much as a clue to what they're really doing.