Doubt on why some syntaxis is not used for PHP

I'm gonna guess that there might be some syntaxis problems or something, since I would guess the following make sense to the PHP language. Arrays: Since the + operator already gives the union of two arrays, why isn't the - operator for differences and | for intersections? I would find those to be rather natural and actually easy to implement. Classes: I was also wondering why the static methods of a class use the :: syntaxis. After all, I don't see what's the problem with also using -> for static calls. Just by adding MyClass->staticMethod(), the whole problem of namespaces and :: as separator would seem to be made a bit easier. Just some questions =) I'm not here to say that things are wrong, just wondering why they weren't thought to be the other way. Again, there might be some syntaxis problem with the parser that I haven't thought so far. Regards, Mamsaac