userid in query

[Lea Verou]

I'm writing a plugin that has a query inside that "filters" the entries from a database field if the userid in the db field matches the user's id (it's a postbit modification). In the query I currently have it as $post[userid]. Should I use something else? I also tried $post['userid'] and even $post["userid"] (lol) but neither worked...

The error I get is Fatal error: Call to a member function on a non-object.