SaranacLake, even though I am probably the worst PHP person on this whole forum, I was fascinated with encryption and hashes, and a few months ago, I spent almost a full month studying PHP encryption! I don't need it for my own site, I just studied it for the same reason I read this forum -- it is fascinating! I learned how to do lots and lots of encryption, very secure encryption, but I also learned that with ONE little mistake, one slip of the code, ONE server misconfiguration, and you might open yourself up to some big lawsuit (ook at all the big multibazillion dollar companies that have been IN THE NEWS for their stupid data breaches! And they TEAMS of encryption geniuses, working for them, and they STILL couldn't get it right. So, it is a fascinating topic! It's fun to learn! But in my opinion, just my opinion, it would be better to hire a reputable first rate security company to do the credit card portion of the code you require. Then, if worse came to worse, and for whatever reason you had a data breach, you won't be in the awkward position of having to say, "well, I proudly did all the security coding myself, all the forums said my algorithm was secure..." :-)
Again, just my opinion.