I would like to make things automated, you know, user enters amount they want to deposit to their account. Press "Pay now", then gets redirected to Paypal, finishes the operation, gets back to website and sees the result.
Thats exactly what paypal does.. Also PayPal has an API - so it doesn't matter what framework you use, it's all just simple calls, and handling the output.. SSL is NOT a requirement for your site actually, as the data exchange would be happening with PayPal and would invoke their SSL.
If you were actually taking users credit card information on YOUR site, you have to meet all of these standards, AND receive their blessing once you've paid for, and passed their security audit.
https://en.wikipedia.org/wiki/Payment_Card_Industry_Data_Security_Standard
Build and maintain a secure network
1. Install and maintain a
firewall configuration to protect cardholder data
2. Do not use vendor-supplied defaults for system
passwords and other security parameters
Protect cardholder data
3. Protect stored cardholder data
4. Encrypt transmission of cardholder data across open, public networks
Maintain a vulnerability management program
5. Use and regularly update anti-virus software on all systems commonly affected by malware
6. Develop and maintain secure systems and applications
Implement strong access control measures
7. Restrict access to cardholder data by business need-to-know
8. Assign a unique ID to each person with computer access
9. Restrict physical access to cardholder data
Regularly monitor and test networks
10. Track and monitor all access to network resources and cardholder data
11. Regularly test security systems and processes
Maintain an information security policy
12. Maintain a policy that addresses information security
