This is sort of interesting, but I'm not sure how it applies to non-black hats. If you are responsible for this code just switch it all to mysqli and be done with it.
1: You cannot call yourself a professional web developer. You can't even call yourself a competent amateur programmer, you are just playing with toys you clearly do not understand.
2: You deserve absolutely no pity when (not if) you get hacked.
If this sounds harsh, it's meant to, this is an incredibly well known problem (and has been for years) and it's incredibly easy to fix.
Besides, I find knowledge useful in a general sense.