I have to use URLs with the following format
index.php?sid=134475&134475X12X361=testwert123123&134475X12X366=2

The URL has to look like this, because the learning management system we are using can only pass url params in that format. (for example course id)

When I change config.php (urlformat path > get):

    'urlManager' => array(
        'urlFormat' => 'path',
        'rules' => require('routes.php'),
        'showScriptName' => true,
    ),

to

    'urlManager' => array(
        'urlFormat' => 'get',
        'rules' => require('routes.php'),
        'showScriptName' => true,
    ),

there is no possibility to login or fill out any survey anymore. Activating error log does not display any errors.