Doctrine: set foreign relation - symfony

Question

This is regarding a problem with Doctrine when I try to insert a record into a associative entity. Below is a simplified description of the problem.
I have two tables, let's call them One and Two. Table One has a foreign key to table Two, called twoId with a column two_id. Field two_id happens to be part of the primary key.
* #ORM\Id
* #ORM\Column(name="user_id", type="string", length=40)
*/
private $twoId;
/**
* #ManyToOne(targetEntity="[...]", inversedBy="[...]", fetch="EAGER")
* #JoinColumn(name="two_id", referencedColumnName="id", onDelete="CASCADE")
*/
private $two;
I am trying to insert a new record into table A. This works:
$two = [.. read from DB ..];
$one = new One();
$one->setTwo($two);
$one->setTwoId($two->getId());
$em->persist($one);
$em->flush();
I don't like to call both setTwo and setTwoId. Furthermore, I don't like reading the $two record before referencing it.
If I skip setTwoId call, I get the error: Entity of type [..] is missing an assigned ID for field 'twoId'. The identifier generation strategy for this entity requires the ID field to be populated before EntityManager#persist() is called.
If I skip setTwo call, I get the error: Integrity constraint violation: 1048 Column 'two_id' cannot be null
My problems are:
How can I avoid calling both setTwo() and setTwoId()?
What if I want to reference a entity from Two without reading it? Should I use $em->getReference()? (PhpStorm doesn't even recognize it)

Answer 1

In case someone makes the same mistake:
As pointed out by #lordrhodos, declaring the field $twoId was wrong because Doctrine will create it automatically without having a definition.
Definition:
/**
* #ManyToOne(targetEntity="[...]", inversedBy="[...]", fetch="EAGER")
* #JoinColumn(name="two_id", referencedColumnName="id", onDelete="CASCADE")
*/
private $two;
Usage:
$two = [.. read from DB ..];
$one = new One();
$one->setTwo($two);
$em->persist($one);
$em->flush();