I'm building simple CMS in S2 and I have little trouble wih processing relational Category in Article form.

Code for CategoryType and action: <http://codepaste.net/ahyoig> all like in tutorial/manual on Symfony site.

Form looks fine, but when i process data (also like in manual) i get error: "Expected argument of type array, string given" in select field and I ahve no idea right now how to solve it.