oneToMany:
    tagPostAssociations:
        targetEntity: MockizartBundleBlogBundleEntityMockblogTagPost
        mappedBy: "post"
        cascade: ["persist","remove"]

oneToMany:
    tagPostAssociations:
        targetEntity: MockizartBundleBlogBundleEntityMockblogTagPost
        mappedBy: "tag"
        cascade: ["persist","remove"]

manyToOne:
    post:
        associationKey: true
        targetEntity: MockizartBundleBlogBundleEntityMockblogPost
        inversedBy: "tagPostAssociations"
    tag:
        targetEntity: MockizartBundleBlogBundleEntityMockblogTag
        inversedBy: "tagPostAssociations"

$post = $this->getDoctrine()->getManager()->find('MockizartBlogBundle:MockblogPost',6);
    $b = $this->getDoctrine()->getManager()->find('MockizartBlogBundle:MockblogTagPost',['tagId' => 20,'postId' => 6]);
    $post->removeTagPostAssociation($b);
    $this->getDoctrine()->getManager()->persist($post);
    $this->getDoctrine()->getManager()->flush();

public function __construct($tag, $post)
{
    $this->tagId = $tag->getId();
    $this->postId = $post->getId();
    $this->post = $post;
    $this->tag = $tag;
}

public  $tagPostAssociations;

public function __construct() {
    $this->tagPostAssociations = new ArrayCollection();
}

public function addTagPostAssociation(MockblogTagPost $tagPostAssociations)
{
    $newTag = $tagPostAssociations;
    $this->newTags[$newTag->getTagId().$newTag->getPostId()] = $newTag;
    $hasTagPost = $this->hasTagPost($newTag);

    if (!$hasTagPost) {
        $this->tagPostAssociations[] = $tagPostAssociations;
    }

    return $this;
}


public function removeTagPostAssociation(MockblogTagPost $tagPost)
{
    $this->tagPostAssociations->removeElement($tagPost);


    return $this;
}

public function getTagPostAssociations()
{
    return $this->tagPostAssociations;
}