Is it possible to create static variables at runtime in PHP?

Suppose a class, foo, has one static variable, bar. Is it possible to write PHP code that will create a new static variable, bar2, for the foo class at runtime?

No, it's not possible.

A static variable is, as its name says, allocated statically at compile time. It cannot be allocated during runtime, nor can it be deallocated (e.g.: unset) during runtime either.

Also, static variables are independent of the call stack.

You can read more on Wikipedia.