If you have made it this far, the chances are the sun will be rising outside shortly and you had best get some sleep before morning! However, hopefully you will have learnt a great deal about the coolest -- and probably least-exploited -- alternative use for PHP.
Creating graphical applications for PHP may, at first, not seem "right", which is quite true to some extent. After all, PHP was designed to be a language for general web use, and not for GUIs. However, once you get over the initial, and indeed inevitable shock of switching to signal-based programming, it is normally a pleasant experience.
The GTK version used with PHP-GTK is quite old, and recent releases have been far superior, with a lot of work done to GTK to make it more flexible, with more intuitive interaction between objects. While GTK2 support is not currently on the card for PHP-GTK, I shall not imagine it will be long. Until then, there is more than enough to get to grips with using the current release of PHP-GTK - good luck!