How to setup a many to many form in Symfony2

Question

I have three entities, ChannelEntity -> MatchChannelEntity <- MatchEntity, the MatchChannelEntity saves the many to many relations between the other two tables, I want a form

Answer 1

Ok, I will close this question. That's because I set up the many to many relation between the two tables wrong, and the correct way is as following(I trimed the code a bit):

Many to many: One match has many channels and one channel has many matches.

Match:

class Match
{
    /**
     * @ORM\ManyToMany(targetEntity="Channel", inversedBy="matches")
     * @ORM\JoinTable(name="match_channels")
     */
    private $channels;

Channel:

class Channel
{
    /**
     * @ORM\ManyToMany(targetEntity="Match", mappedBy="channels")
     */
    private $matches;    

Doctrine will automatically create the cross reference table for you, named MatchChannels. Note the JoinTable annonation, it is very important.

And when you done, you can create a many to many form easily, just like you create other type of forms/fields.