title: Eloquent select items with several where clause on same relationship column
body: <p>I have a User model with a hasMany relations to model Cart.</p>
  
  <p>Cart model has (among others) user_id and campaign_id.</p>
  
  <p>I want to make a request which will grab all the users who have a cart with a specific campaign_id and also at least one of a list of campaign ids.
  I came up with this request </p>
  
  <pre><code>$alistUsers = User::whereHas('cart', function($query) use($campaignId, $campaignIds){
                              $query-&gt;whereIn('campaign_id', $campaignIds)
                                      -&gt;where('campaign_id', '=', $campaignId)
                              ;
                          })
                          -&gt;get()
                          ;
  </code></pre>
  
  <p>which obviously returns 0 results since a cart item can't have several campaign_id.</p>
  
  <p>I probably need to do something with sub selects but I can't find the correct answer.</p>
  
  <p>If someone has an idea I'm all ears.</p>
  
  <p>Thanks.</p>