Andi Gutmans has pointed out an effort that Adobe has proposed that would go a long way towards adding AMF support to the Zend Framework.
This ZF component will allow for client-side applications built with Flex and Adobe AIR to communicate easily and efficiently with PHP on the server-side. Leading the design of the component for Adobe is Wade Arnold. Wade already has a track record of bringing the Adobe RIA technologies to PHP as a result of all of his work on AMFPHP.
Andi sees this as a next logical step to helping the framework become more "Enterprise oriented" and to compliment the recent Dojo integration. The plan is to release it with the 1.7 version of the framework, but the actual timing may vary due to the approval process.