In 1985 after about two years of full time programming I had an epiphany; realising that global variables are a very bad idea. Roughly 20% of the bugs that I kept finding were down to abuse or misuse of global variables, so I stopped using them, apart from the time when you really should use one (e.g. for a pointer to global shared memory that never changes).
So here I am over 20 years later, and I've just realised exactly the same thing, except this time it's in PHP not 'CORAL' '66'.