You’ve come to a real watershed moment in your programming career. Up until now, you’ve been using a lot of PHP constructs—from if statements to some basic functions to constants and even error handling—and have gotten familiar with the basic MySQL interactions you’ll need in typical PHP scripts. With what you already know, you’re ready to take on most of the basic programming problems you’ll run across in a typical web application, as long as you’re thinking on a single-page level.

In other words, if you’ve got a form that gathers information, you can handle that. You can grab information from a table, and put information into a table, too. No problems there; you can respond to errors, redirect users, and even distinguish between a good user experience and a bad one.