Heya, maintainer of the PHP client here.
I believe that exception is actually being generated by PHP itself, not the client. By default, most PHP installations only allow scripts to run for 30-60 seconds before it is forcefully terminated, as a protection against long-running or abusive scripts.
You can change the timeout value in your php.ini file, under the max_execution_time setting. You can also set these values dynamically in the script (set_time_limit(...) and ini_set('max_execution_time',...), see http://us2.php.net/manual/en/function.set-time-limit.php). But they may be limited by the max value in the php.ini file, I'm not sure.