empty response on model using union - cakephp-3.0

Question

I have the following code
public function findAccessible(Query $query, array $options){
return $this->findPublic($query, $options)
->union($this->findMyAdmin($query, $options));
}
public function findPublic(Query $query, array $options){
return $query
->where(['public' => true]);
}
public function findMyAdmin(Query $query, array $options){
return $query
->where(['admin_user_id' => $options['User.id']]);
}
The findAccessible call gives me this error message in Chrome: ERR_EMPTY_RESPONSE
No other error message, no entry in error log. I am sure that is because of the union call. How to do it?
What I want to achieve:
groups hasAndBelongsTo users
groups: id, name, admin_user_id, public
I would like to get groups
1) what are public groups (This is ok, findPublic method)
2) where admin_user is the given user (This is ok, findMyAdmin method)
3) in where the given user is a member (This is ok, I could do it with an other find()->matching call)
4) which are accessible for the user, eg. public OR the given user is admin OR a member - meaning the union of 1), 2) and 3) - that is with what I am struggling. If I put all these to one find method I can not define OR relationship for the membership, as that is done by matching what is translated into an inner join.

Answer 1

I found a really ugly but working solution.
public function findAccessible(Query $query, array $options){
$qq = $this->query($query);
$memberships = $qq->matching('Users', function($q) use ($options){
return $q->where(['Users.id' => $options['User.id']]);
});
foreach($memberships as $m){
$memberInGroup[] = $m->id;
}
return $query
->where(['public' => true])
->orWhere(['admin_user_id' => $options['User.id']])
->orWhere(['Groups.id IN' => $memberInGroup]);
}
I hope somebody will find a better solution and post here.