$ modx-> db-> select() Problem

Modx revo 2.2
I'm trying to make a snippet to get the value "vote_total" from the database "modx_star_rating":

$ docId = $ modx-> resource-> get ('id');
$ result = $ modx-> db-> select ("vote_total, $ modx-> db-> getFullTableName ('modx_star_rating'), star_id = docId");
$ vote = $ modx-> getValue ($ result);
echo $ vote;

Either get a syntax error on the symbol "="

or

Call to a member function select () on a non-object
How to make a request $ modx-> db-> select ()?
What may be my problem?