Custom php web form creation, with database creation / integration and Paypal integration

Hi everyone, I've developed an html and css website, but I need a web form (with some non-standard features) and database created / developed. The form itself won't have many more than 10-15 fields, but it needs to write entries securely into a database (which needs creating), and I'd like some custom features to the form, obvious things like certain fields must be in a certain format, certain fields must be filled in, but also in at least two instances, for example, if radio button B is selected, a new field appears for more input. Also, dependent on one (or two) seperate radio button selections, the paypal link at the bottom of the form changes code, to enable different prices available, which would work with the Paypal API. Essentially there would be six 'packages' to pick from. Think that's it - I can handle html and css so design wouldn't be a priority. I may handle the database creation myself but will talk more with you about that once we begin. Thanks!