Doctrine 2 and Many-to-many link table with an extra field

A Many-To-Many association with additional values is not a Many-To-Many, but is indeed a new entity, since it now has an identifier (the two relations to the connected entities) and values.

That's also the reason why Many-To-Many associations are so rare: you tend to store additional properties in them, such as sorting, amount, etc.

What you probably need is something like following (I made both relations bidirectional, consider making at least one of them uni-directional):

Product:

namespace Entity;use Doctrine\ORM\Mapping as ORM;/** @ORM\Table(name="product") @ORM\Entity() */class Product{    /** @ORM\Id() @ORM\Column(type="integer") */    protected $id;    /** ORM\Column(name="product_name", type="string", length=50, nullable=false) */    protected $name;    /** @ORM\OneToMany(targetEntity="Entity\Stock", mappedBy="product") */    protected $stockProducts;}

Store:

namespace Entity;use Doctrine\ORM\Mapping as ORM;/** @ORM\Table(name="store") @ORM\Entity() */class Store{    /** @ORM\Id() @ORM\Column(type="integer") */    protected $id;    /** ORM\Column(name="store_name", type="string", length=50, nullable=false) */    protected $name;    /** @ORM\OneToMany(targetEntity="Entity\Stock", mappedBy="store") */    protected $stockProducts;}

Stock:

namespace Entity;use Doctrine\ORM\Mapping as ORM;/** @ORM\Table(name="stock") @ORM\Entity() */class Stock{    /** ORM\Column(type="integer") */    protected $amount;    /**      * @ORM\Id()     * @ORM\ManyToOne(targetEntity="Entity\Store", inversedBy="stockProducts")      * @ORM\JoinColumn(name="store_id", referencedColumnName="id", nullable=false)      */    protected $store;    /**      * @ORM\Id()     * @ORM\ManyToOne(targetEntity="Entity\Product", inversedBy="stockProducts")      * @ORM\JoinColumn(name="product_id", referencedColumnName="id", nullable=false)      */    protected $product;}

Doctrine handles many-to-many relationships just fine.

The problem that you're having is that you don't need a simple ManyToMany association, because associations can't have "extra" data.

Your middle (stock) table, since it contains more than product_id and store_id, needs its own entity to model that extra data.

So you really want three classes of entity:

• Product
• StockLevel
• Store

and two associations:

• Product oneToMany StockLevel
• Store oneToMany StockLevel