Yes I am using php on the server side to update a database when the user send a form
At this point, that's it IMHO. I wouldn't even use an ELB or auto-scaling at this point.
If you need help, drop a mail, I have spare time I can help you with the specifics (free of charge ofc).
ps. AWS has a learning curve and is not cheap but saves you a great deal of sysadmin management and most importantly, saves you from probable fire-fighting at this stage, plus there is the free tier will get you nearly a year without charges.