title: Polymorphic association to different owner objects in Doctrine 2
body: <p>is it possible to use kind of polymorphic association to different <strong>owner</strong> objects in Doctrine 2? I mean that for example ImageGroup entity is owned by different entities: Article, Album, Post, Comment, etc. So there should be "ownerId" and "ownerType" attributes in ImageGroup table, where "ownerType" is discriminator.</p>
  
  <p>I am already using <strong><a href="http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/inheritance-mapping.html#class-table-inheritance">Class Table Inheritance</a></strong> and also <strong><a href="http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/inheritance-mapping.html#mapped-superclasses">Superclass mapping</a></strong> on other object relationships in my project, but any of them suits for this problem, if I am correct. Because in these situations referred objects are inherited.</p>
  
  <p>I have read answers to polymorphic associations here, but I found no answer to my example.</p>
  
  <p>In my example is no inheritance at all. Any help, please? Thanks in advance!</p>