ZF-11093: Zend_Json_Server always returns error = null
Perhaps in the version 1 of the JSON-RPC spec this was the correct method. However, in version 2 of JSON-RPC:
error This member is REQUIRED on error. This member MUST NOT exist if there was no error triggered during invocation.
I've made my client work around this rather than altering the ZF code, but it would nice to have Zend_Json_Server conform to the spec.