The Joomla! Framework is mostly compatible with external frameworks. However when the framework loads by default, the libraries/joomla/import.php file actions a clean of the request variables. This can have detrimental impact upon any framework loaded into memory prior to Joomla! as their variables in global scope can be destroyed.
The solution to this is when you are loading up Joomla! to define the "_JREQUEST_NO_CLEAN" when loading the framework. This was fixed with #21772, see [].
// Define JRequest::clean to protect our variables! define('_JREQUEST_NO_CLEAN', 1); // basic to make J! happy define('_JEXEC', 1); //make j! happy define('JPATH_BASE', dirname(__FILE__)); define('DS', DIRECTORY_SEPARATOR); // Load up the standard stuff for testing require_once JPATH_BASE.DS.'includes'.DS.'defines.php'; require_once JPATH_BASE.DS.'includes'.DS.'framework.php';