[fw-webservices] Looking for jsonrpc client

I have an application in which a Zend Framework client communicates with
a server via XMLRPC, using the ZF xmlrpc client. I want to convert to
using JSON. Does anyone know of a JSONRPC client, either within ZF or
just a PHP implementation? (The ZF library includes a server, but not a
client.)

TIA,

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Don Dwiggins
Advanced Publishing Technology