I want to develop some functionality: a "3-step-system" which will consist of 3 pages.**
1) In the first page the personal information of his customers will be collected,
2) In the second page, customers must answer to some questions,
3) In the third page, customers may select some of his products (his list has only 2-3 products to select and they are static products) and then they must pay via PayPal. At the end of the transaction e-mails must be sent to his clients and to himself.
All data must be registered in the database (MySQL). There is no need of HTTPS/SSL encryption.
I have an idea of how to develop this system in pure PHP language (on php script files). But how can I develop this inside Joomla!? Can the Joomla run pure PHP script files?
Do I am forced to make this only as an extension of Joomla!? If so, what kind of extension?