symfony - Symfony2 Why Doctrine remove my element when I remove it from the collection? -

given have 2 entities, post , comment

my relations :

post

onetomany:     comments:         targetentity: comment         mappedby: post         orphanremoval: false         cascade: [ persist ]         fetch: extra_lazy 

comment

manytoone:     post:         targetentity: post         joincolumn:             name: post_id             referencedcolumnname: id             ondelete: set null 

now in controller, whenever want manually remove comment post, doctrine deletes comment database.

public function testaction() {     $postrepository = $this->getdoctrine()                    ->getmanager()                    ->getrepository('mybundle:post');      $post = $postrepository ->find(1);      $commentrepository = $this->getdoctrine()                    ->getmanager()                    ->getrepository('mybundle:comment');      $comment = $commentrepository ->find(1);      /* comment child of post */     $post->removecomment($comment);     }   /* entity/post */ public function removecomment(comment $comment) {      $this->comments->removeelement($comment); } 

by doing that, comment deleted database, don't it.

ps : found solution avoid doctrine deleting entity :

foreach($post->getcomments() $_comment) {     if ($commment === $_comment) {         $post->removecomment($comment);     } } 

in case doctrine didn't deleted comment , removed relation want. can explain me please ?

thanks