Inheritance Mapping and Many-To-One Relation - orm

Question

I made an abstract Upload class with 4 different children.
The classes UploadCompanyPic, UploadCompanyLogo and UploadUserPic are one-to-one relations, but the UploadPostFile has to be Many-to-one (one post has many uploaded files), I want to use alle the functions that are in the abstract class, but I can't get the Many-to-one relation to work.
This is what I have since now:
<?php
namespace AppBundle\Entity\Upload;
use Doctrine\ORM\Event\LifecycleEventArgs;
use Doctrine\ORM\Mapping as ORM;
use AppBundle\Util\Registry;
use Symfony\Component\HttpFoundation\File\UploadedFile;
/**
* Abstract Class Upload
*
* #package AppBundle\Entity\Upload
*
* #ORM\MappedSuperclass()
* #ORM\Entity(repositoryClass="AppBundle\Repository\Upload\UploadRepository")
* #ORM\HasLifecycleCallbacks()
* #ORM\Table(name="upload", indexes={
* #ORM\Index(name="idx_cat_id", columns={"category","foreign_id"})
* }
* )
* #ORM\InheritanceType("SINGLE_TABLE")
* #ORM\DiscriminatorColumn(name="category", type="string")
* #ORM\DiscriminatorMap({"company-pic" = "UploadCompanyPic", "user-pic" = "UploadUserPic", "company-logo" = "UploadCompanyLogo", "post-file" = "UploadPostFile"})
*/
abstract class Upload
{
/**
* #ORM\Id
* #ORM\GeneratedValue(strategy="AUTO")
* #ORM\Column(name="id", type="integer", length=255, nullable=false)
*/
protected $id;
protected $foreignId;
/**
some more code
* #return mixed
*/
public function getForeignId()
{
return $this->foreignId;
}
/**
* #param mixed $foreignId
*/
public function setForeignId($foreignId)
{
$this->foreignId = $foreignId;
}
UploadCompanyPic:
<?php
namespace AppBundle\Entity\Upload;
use Doctrine\ORM\Mapping as ORM;
use AppBundle\Entity\Upload\Upload as Upload;
/**
*
* #ORM\Entity
*
*/
class UploadCompanyPic extends Upload
{
protected $category="company-pic";
/**
* this is the foreign id of the mapped entity
* #ORM\Column(name="foreign_id", type="integer", length=255, nullable=false)
*/
protected $foreignId;
}
(Upload CompanyLogo and UploadUserPic look the same)
<?php
namespace AppBundle\Entity\Upload;
use AppBundle\Entity\Blog\Post;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\ORM\Mapping as ORM;
use AppBundle\Entity\Upload\Upload as Upload;
/**
*
* #ORM\Entity
*
*/
class UploadPostFile extends Upload
{
protected $category="post-file";
/**
* ManyFiles have one Post
* #ORM\ManyToOne(targetEntity="AppBundle\Entity\Blog\Post", inversedBy="files")
* #ORM\JoinColumn(name="foreign_id", referencedColumnName="id")
*/
protected $foreignId;
/**
* #return ArrayCollection
*/
public function getForeignId()
{
return $this->foreignId;
}
/**
* #param Post $foreignId
*/
public function setForeignId($foreignId)
{
$this->foreignId = $foreignId;
}
}
Any suggestions for me? Thanks!

Answer 1

One my colleagues found an answer:
/**
* Abstract Class Upload
*
* #package AppBundle\Entity\Upload
*
* #ORM\MappedSuperclass()
* #ORM\Entity(repositoryClass="AppBundle\Repository\Upload\UploadRepository")
* #ORM\HasLifecycleCallbacks()
* #ORM\Table(name="upload", indexes={
* #ORM\Index(name="idx_cat_id", columns={"category","foreign_id"})
* }
* )
* #ORM\InheritanceType("SINGLE_TABLE")
* #ORM\DiscriminatorColumn(name="category", type="string")
* #ORM\DiscriminatorMap({"company-pic" = "UploadCompanyPic", "user-pic" = "UploadUserPic", "company-logo" = "UploadCompanyLogo", "post-file" = "UploadPostFile", "partner-logo" = "UploadPartnerLogo"})
*/
abstract class Upload