more information about the php-/zend-api

Hi folks, I'm currently trying to work my way through an extension. Using the tutorials on the php.net/zend.com ... and other sites it works so far to do some work, return values and getting parameters. But how can I get access to the variables defined in php or add other variables without the need to return them and so on. There must be anywhere more information about such matters or am I just blind? Thanks in advance, Thomas