Problem saving from inversed side of many-to-many relationship - php

Question

I have two entities: AudioPlaylist and AudioTrack.
AudioPlaylist.php:
/**
* #ORM\ManyToMany(targetEntity = "AudioTrack", inversedBy = "audioPlaylists")
* #ORM\JoinTable(name = "audioplaylist_audiotrack")
*
* #var ArrayCollection
*/
protected $audioTracks;
AudioTrack.php:
/**
* #ORM\ManyToMany(targetEntity = "AudioPlaylist", mappedBy = "audioTracks")
*
* #var ArrayCollection
*/
protected $audioPlaylists;
My problem is that when I call $audioTrack->addAudioPlaylist($audioPlaylist), the audioplaylist_audiotrack table doesn't get updated. I'm expecting a new row to be added to the table signifying the relationship between the two entities. Everything works fine for the inverse though $audioPlaylist->addAudioTrack($audioTrack) adds a new row.
I'm making sure to persist $audioTrack and flush the entity manager, but no luck, so I assume there must be something wrong with my annotations (I'm using this example from the Doctrine docs). Any ideas?

Answer 1

This is probably because you have not set the cascade property for your inverse side. You must define cascading explicitly for Doctrine2 to persist any related entities.
/**
* #ORM\ManyToMany(targetEntity = "AudioPlaylist",
* mappedBy = "audioTracks",
* cascade = {"persist", "remove"})
*
* #var ArrayCollection
*/
protected $audioPlaylists;
Make sure you also add your AudioTrack to AudioPlaylist as well, when calling AudioTrack::addAudioPlaylist():
public function addAudioPlaylist(AudioPlaylist $playlist)
{
$this->getAudioPlaylists()->add($playlist);
$playlist->getAudioTracks()->add($this);
}