$xml = new SimpleXMLElement($feed_in);
       //pull out the calls
       /*
        * <multifunction>
        *   <call>
        *       <module>calling module's integer id</module>
        *       <id>module's internal reference</id>
        *       <function>function name</function>
        *       <par id='parameter number'>argument</par>
        *       <par ... >
        *   </call>
        *   <call ... >
        * </multifunction>
        */
       $numCalls = $xml->xpath("count(/multifunction/call)");