Thread: Why can I modify my static class member?

I wrote a class with a privated static memeber:
i.e. static int x.

I initialized the member outside the class.

Now I have a function that reads like this:

int& CLASSTYPE operator[](int);

basically this function will return the class member.
but when i created an object of the class say "obj"
and wrote

obj[integerhere]=5;

it actually modified my static data member!!!

What should I do? I'm lost and confused!