The guy behind dotdeb.org does great work. I personally wouldn't have any reservations about using his repo.
If you want to do the work yourself, then you should look into taking the official packages from the unstable repos (
http://packages.debian.org/sid/php5) and "backporting" them to your stable version.
This can be as simple as changing one or two words and recompiling. That is assuming that the updated version does everything you want, and that no package dependency problems are introduced with the new version.
If you need something different than the updated stock package, then you can start learning how to edit the package. The dotdeb.org packages sometimes have changes from the stock Debian packages.
A common scenario is where you use nginx but you want to use a third party module like cache-purge. nginx requires recompiling to add modules.