gistfile1.php

  class User {
    
    ...
    
    public function sites() {
        return $this->hasManyThrough('Site', 'Account');
    }

    public function hasSite($site) {
        return $this->sites()->whereId($site->id)->count() != 0;
    }
  }
  
  // Elsewhere...
  // the following says that the 'id' clause in the were is ambiguous
  // (both models have an ID) - how can I cause my search to be constrained
  // to if the user is distantly related to the Site model with the given ID?!
  echo User::first()->hasSite(Site::first());