symfony Doctrine link 添加一对多关联记录

例子：

User(table)
————
id:~
——————
Book(table)
————
id:~
user_id(fk)
——————

添加一个user和他的藏书
1.

$u=new User();
$u->name = 'lag'
$u->save();
------------------
$b=new Book();
$b->name = 'lag book';
$b->save();
$b->link('User',array($u['id']));

2.

$u=new User();
$u->name = 'lag';
$u->Book[]->name = 'lag book';
$u->save();

3.

$bookids = array();
$b1= new Book();
$b1->name = 'book1';
$b1->save();
$bookids[]=$b1['id'];

$b2= new Book();
$b2->name = 'book2';
$b2->save();
$bookids[]=$b2['id'];

$u=new User();
$u->name = 'lag'
$u->save();

$u->link('Book',$bookids);