Both Yii and Yii2 have url management and routing built in. They will compare the url of the request to a list of rules you’ve defined.
Sometimes you might want to do various checks of the url in yii config main and then send every other request to a particular controller.
The rule you need to add last to the urlManager is…
'(.*)' => 'controller/action',
… and now any rule that isn’t matched previously will end up being sent to your defined controller and action.
In Yii2 you can also do the same:
'<url:(.*)>' => 'controller/action'