Fatal error: Cannot redeclare class Zend_Exception

I have setup webservice for the school and it was running ok till the time. I am using moodle 2.1+ and recently I have changed the php version as below....

PHP 5.4.9 (cli) (built: Dec 11 2012 01:45:57) , Zend Engine v2.4.0, with XCache v3.0.0, Copyright (c) 2005-2012, by mOo with XCache Cacher v3.0.0, Copyright (c) 2005-2012, by mOo with XCache Coverager v3.0.0, Copyright (c) 2005-2012, by mOo

Now when I try the Site administration > Development > Web service test client it used to work ok and returns the data....

BUT NOW IT GIVES THIS ERROR .....

URL: https://SCHOOL-WEBSITE-URL:443/saas/3rdparty/moodle2/webservice/xmlrpc/server.php?wstoken=0c7eb048fc4b2defER323e0e23d9f6e