How do I get the exception object in a catch block ?

Hi, I am calling some PHP code from my extension, and this code can generate exceptions. I put the call_user_function call in a zend_try/zend_catch block, and my question now is : in the zend_catch block, how do I access the exception object ? This would allow me to differentiate between several exception classes, and retrieve the exception's message. If you know an example in a PECL extension, just tell me. Or, maybe I am wrong and zend_try/zend_catch does not work this way ? Thanks in advance Francois