require all values in array to be matched when using where_in

[eluser]Andy UK[/eluser]
I tried the following, but after adding a second value to the array, i'm getting no results. Even though both feature ids appear together for a number of properties:

Code:

foreach($this->session->userdata('selected_features') as $feature)
   {
    $this->db->where('feat_prop_join.feature_id', $feature);
   }