title: How to relate entities in Symfony 2 and Doctrine?
body: <p>How can i create a relationship between entities with Symfony 2 and Doctrine? I'm only able to create standalone entities. Maybe someone can help me figure this out using the entity generator? I want to:</p>
  
  <ul>
  <li>Create two entities: Post and Category. A Post is part of a Category.</li>
  <li>Create a Tag entity: A Post can have many Tags.</li>
  </ul>