You'll want to look into sessions as well, for storing the answers between page loads. Or, more specifically, identifying a user across multiple page views.
Right, and I'm sure all that ties into membership logins with MySQL, of which I'm wondering if I could further simplify the set up of by copying a readily available membership script on the web, and by treating MySQL as a flat file with one table rather than an actual database with many tables and relationships - just for now. That, I'm thinking, would allow me to focus on the sequences of questions that I am interested in asking without getting too bogged down into technical details at first.
The idea behind the application is to continuously and systematically ask the end user as many questions as they will allow over time as to measure compatibility, and reveal insights that will help not only themselves, but also others in reaching desired relationship outcomes.
For example, if a guy's answers indicate that he "kicks puppies, and is mean to little kids", helpful feedback could be that 99% of female users on the system indicate finding this unacceptable, and that by changing his ways, he could improve his chances with women in general by a high margin. Perhaps a certain type of guy indicates interests in things like "BDSM", "Knife Play", and "Non-Consent", and a woman wonders why the guys she meets online come off as being like Jack the Ripper. It's probably because she's attracting the wrong type of guys, where the website could indicate that X % of the time this can be expected based upon the experiences other women have reported upon meeting a person with these types of interests. Similarly, to the guy that is into BDSM that wonders why said woman will not return his calls after giving her the scare of her life, it could be statistically pointed out that he may have greater success with women who not only share his particular interest in BDSM, but who are actually turned on by it. Another possibility is that a guy doesn't follow-up with a woman he's gone on a date with until two weeks later, and wonders why she doesn't return his call. Statistically it can be shown that that most women are going to be more high maintenance than that based on the answers other users have provided. This kind of thing is what I'd be interested in getting to a point where I can focus on before moving on to a more comprehensive study of programming if I can.
That being said, I'd imagine the single most common line of PHP code I'd be writing in this type of application would be IF statements since so much of it would be focused on sequences of questions.