Thanks, Andrew.
I changed the context, but it made no difference in output. When I telnet to AMI, the following works perfectly:
ACTION: Originate
CallerID: 14408
Channel: SIP/335298@10.44.1.11
Context: ext-local-custom
Exten: 231144808
Priority: 1
The call completes correctly. Now I just need to do that in PHP. Do you have an examples of using $astman->Originate($call_data); ? Is my array OK as a param for $astman?