What is the owning side and inverse side in the doctrine 2 doc example

Question

On this page of association mapping, there's an example in the manytomany section. But I don't understand which entity (group or user) is the owning side.

http://docs.doctrine-project.org/en/2.0.x/reference/association-mapping.html#many-to-many-bidirectional

I've put the code here too

<?php
/** @Entity */
class User
{
    // ...

    /**
     * @ManyToMany(targetEntity="Group", inversedBy="users")
     * @JoinTable(name="users_groups")
     */
    private $groups;

    public function __construct() {
        $this->groups = new \Doctrine\Common\Collections\ArrayCollection();
    }

    // ...
}

/** @Entity */
class Group
{
    // ...
    /**
     * @ManyToMany(targetEntity="User", mappedBy="groups")
     */
    private $users;

    public function __construct() {
        $this->users = new \Doctrine\Common\Collections\ArrayCollection();
    }

    // ...
}

Do I read this annotation like this: User is mappedBy groups so group is the entity that does the connection management, thus the owning side?

Also, I've read this in the docs:

For ManyToMany bidirectional relationships either side may be the owning side (the side  that defines the @JoinTable and/or does not make use of the mappedBy attribute, thus using   a default join table).

This lets me think that User would be the owning side as the JoinTable annotation is defined in that entity.

Answer 1

But I don't understand which entity (group or user) is the owning side

The User entity is the owner. You have the relation of groups in User:

/**
 * @ManyToMany(targetEntity="Group", inversedBy="users")
 * @JoinTable(name="users_groups")
 */
private $groups;

Look above, $groups var contains the all groups associated to this user, but If you notice the property definition, $groups var has the same name of mappedBy value (mappedBy="groups"), as you did:

/**
 * @ManyToMany(targetEntity="User", mappedBy="groups")
 */
private $users;

What does mappedBy mean?

This option specifies the property name on the targetEntity that is the owning side of this relation.