title: Doctrine 2 entities relationships: cascade merging
body: <p>I manage complex entities, with multiple and different relationships with other entities, which themselves are linked to multiple other entities sometime.</p>
  
  <p>I am making an edit form, and would like to avoid having to code manually different Doctrine 2 queries to udpate every entity linked to the modified entity.</p>
  
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  <p>Is it possible to cascade merge entities in Doctrine 2 ? By that, I mean modifying an entity and its linked entities (<strong>oneToMany</strong>, <strong>ManyToMany</strong>... relationships) and then applying the changes to the entity and the linked entities in cascade.</p>
  
  <p>If not, what is the 'clean' way to apply modifications to all the concerned entities ? Does it need to be manually done, by calling merge or update on every entity ?</p>