self:: vs this

Hy people, I have an existential doubt regarding php classes. I have been a php programmer for quite a long time, but never could figure out the clear difference between using this-> or self:: when calling member functions, wether they are private or public. I used them indistinctly and seemed to sort the same effects, although, when working with statics classes, self:: was the only way to access members. Well, that's all, any can put me some light on the matter? Thanks, -- Mariano Guadagnini UVCMS S.R.L www.uvcms.com