retrieving and setting vars from own extension?

Hi folks,

sorry but I couldn't find the answer in the docs at php.net
and google didn't turn out anything usefull to.

I'm trying to write my own extension which would need to retrieve
and set (global) variables for the php-script its called from.

But I just can't find a way to do this in the docs.
Could you point me into the right direction?

Btw. are there any more docs on the zend-api available
than the section in the php.net-manual?

Thanks,

Thomas