Look, I'm not trying to personally attack you I'm just giving you brutal criticism and I apologise if I'm coming across as an idiot. I can't see the reason as to why you posts are being deleted (it just says "Thread cleanup"), I don't moderate this section anymore so I can't see your deleted posts.
I swear to you, it's your website information using the Developer Tools in chrome. I just redid it on my laptop and it's at 13.29 seconds for a complete page load and my internet is fine, I do blame most of it to the static files Sulake made (they're awful). As for the code (etc.) here are a few tips;
- Use a framework, it makes life so much easier and in professional environments they use frameworks just because there's no need to re-invent the wheel.
- If you're writing a small personal script which you aren't releasing, classes in one file is fine. For public releases use your own custom made (preferably MVC framework) or just use one of the many frameworks available. There's no point re-inventing the wheel. Thus you avoid having 10,000 questions and they can fix it themselves easier.
- Go absolutely ballistic about security. Even Gooby (Gaby) picked up on a few exploits and she's a trap.
- Absolutely avoid 'SELECT *' in queries.
- Keep the HTML mixing with the PHP to a minimum, it was horrendous when I was looking through the code.
- I also noticed in some places your code consistency was off. You were probably tired while writing it, idk.
- USE PREPARED STATEMENTS. Cannot stress this enough.
- I'm not too sure what password hashing you're using but if it's MD5 or SHA1, change it. I recommend using the built in PHP function to handle passwords.
- CSRF protection is an absolute must. Frameworks can handle this for yoooouuuuu, another benefit there.
- Minify your static files and absolutely make sure they're up to date.
- As for the database driver (unsure as to what you were originally using), PDO is my personal recommendation.
- Follow the PSR standard.
There's tons more I could list through but I just don't have the time. From what I can tell as well, the v1 system is no where near fit for a live environment.
I'm being serious about ignoring your lecturers on the store all classes in one file. You may think it's messy to have one class per file but it's a lot easier to manage in terms of code updates and more, version controlling is so much easier as well, on top of that PHP will have to load the entire file into memory (even if it only needs one or two things at that particular time), if you get more developers on this project it will also be difficult for them to get to grips with the system. Which of course could all be fixed if you used a public framework (e.g. CakePHP).
I probably got things mixed up in some cases but I'm exhausted from a long day at work so you'll have to excuse me there.