Just to clarify, I've worked in this business. You can set something up and test it in sandbox mode with every payment processor I've worked with. That's the proper approach for a "side project." What blows my mind is having this set up and accessible to the public. It's just amazingly naive. I don't mean to beat up on you, OP, but you really should shut this thing down. Systems like this are monitored 24x7 for fraudulent activity. You're not really prepared to be in this business yet.