Symfony2 entity problem

DefaultController.php

$entityManager = $this->getDoctrine()->getEntityManager();

        $user = new User();
        $user->setAddress("Khulna");
        $user->setBio("Good guy!");
        $user->setEmail("masnun@gmail.com");
        $user->setName("Masnun");
        $user->setIdentityProvider("facebook");
        $user->setProviderId("masnun");
        $user->setPhone("8801711960803");


        $skype = new Handle();
        $skype->setServiceName("skype");
        $skype->setHandle("phpge3k");

        $twitter = new Handle();
        $twitter->setHandle("masnun");
        $twitter->setServiceName("twitter");

        // WORKS

        $twitter->setUser($user);
        $skype->setUser($user);

       
         //DOESN'T WORK
        /*
        $user->addHandle($skype);
        $user->addHandle($twitter);
        */


        $entityManager->persist($skype);
        $entityManager->persist($user);
        $entityManager->persist($twitter);

        $entityManager->flush();

        return $this->render("WeCodePHPHomeBundle:Default:index.html.twig");

Handle.php

<?php
namespace WeCodePHP\HomeBundle\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity
 * @ORM\Table(name="handles")
 */
class Handle
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @ORM\Column(type="string", length=100)
     */
    protected $service_name;

    /**
     * @ORM\Column(type="string", length=100)
     */
    protected $handle;

    /**
     * @ORM\ManyToOne(targetEntity="User", inversedBy="handles")
     * @ORM\JoinColumn(name="user_id", referencedColumnName="id")
     */
    protected $user;



    /**
     * Get id
     *
     * @return integer 
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Set service_name
     *
     * @param string $serviceName
     */
    public function setServiceName($serviceName)
    {
        $this->service_name = $serviceName;
    }

    /**
     * Get service_name
     *
     * @return string 
     */
    public function getServiceName()
    {
        return $this->service_name;
    }

    /**
     * Set handle
     *
     * @param string $handle
     */
    public function setHandle($handle)
    {
        $this->handle = $handle;
    }

    /**
     * Get handle
     *
     * @return string 
     */
    public function getHandle()
    {
        return $this->handle;
    }

    /**
     * Set user
     *
     * @param WeCodePHP\HomeBundle\Entity\User $user
     */
    public function setUser(\WeCodePHP\HomeBundle\Entity\User $user)
    {
        $this->user = $user;
    }

    /**
     * Get user
     *
     * @return WeCodePHP\HomeBundle\Entity\User 
     */
    public function getUser()
    {
        return $this->user;
    }
}

User.php

<?php
namespace WeCodePHP\HomeBundle\Entity;

use Doctrine\ORM\Mapping as ORM;
use Doctrine\Common\Collections\ArrayCollection;


/**
 * @ORM\Entity
 * @ORM\Table(name="users")
 */
class User
{
    /**
     * @ORM\Id
     * @ORM\Column(type="integer")
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @ORM\Column(type="string", length=100)
     */
    protected $name;

    /**
     * @ORM\Column(type="string", length=100)
     */
    protected $email;

    /**
     * @ORM\Column(type="string", length=100)
     */
    protected $identity_provider;

    /**
     * @ORM\Column(type="string", length=100)
     */
    protected $provider_id;


    /**
     * @ORM\Column(type="string", length=100)
     */
    protected $phone;

    /**
     * @ORM\Column(type="text")
     */
    protected $address;


    /**
     * @ORM\Column(type="text")
     */
    protected $bio;


    /**
     * @ORM\OneToMany(targetEntity="Handle", mappedBy="user")
     */
    protected $handles;

    public function __construct()
    {
        $this->handles = new ArrayCollection();
    }


    /**
     * Get id
     *
     * @return integer
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Set name
     *
     * @param string $name
     */
    public function setName($name)
    {
        $this->name = $name;
    }

    /**
     * Get name
     *
     * @return string
     */
    public function getName()
    {
        return $this->name;
    }

    /**
     * Set email
     *
     * @param string $email
     */
    public function setEmail($email)
    {
        $this->email = $email;
    }

    /**
     * Get email
     *
     * @return string
     */
    public function getEmail()
    {
        return $this->email;
    }

    /**
     * Set identity_provider
     *
     * @param string $identityProvider
     */
    public function setIdentityProvider($identityProvider)
    {
        $this->identity_provider = $identityProvider;
    }

    /**
     * Get identity_provider
     *
     * @return string
     */
    public function getIdentityProvider()
    {
        return $this->identity_provider;
    }

    /**
     * Set provider_id
     *
     * @param string $providerId
     */
    public function setProviderId($providerId)
    {
        $this->provider_id = $providerId;
    }

    /**
     * Get provider_id
     *
     * @return string
     */
    public function getProviderId()
    {
        return $this->provider_id;
    }

    /**
     * Set phone
     *
     * @param string $phone
     */
    public function setPhone($phone)
    {
        $this->phone = $phone;
    }

    /**
     * Get phone
     *
     * @return string
     */
    public function getPhone()
    {
        return $this->phone;
    }

    /**
     * Set address
     *
     * @param text $address
     */
    public function setAddress($address)
    {
        $this->address = $address;
    }

    /**
     * Get address
     *
     * @return text
     */
    public function getAddress()
    {
        return $this->address;
    }

    /**
     * Set bio
     *
     * @param text $bio
     */
    public function setBio($bio)
    {
        $this->bio = $bio;
    }

    /**
     * Get bio
     *
     * @return text
     */
    public function getBio()
    {
        return $this->bio;
    }

    /**
     * Add handles
     *
     * @param WeCodePHP\HomeBundle\Entity\Handle $handles
     */
    public function addHandle(\WeCodePHP\HomeBundle\Entity\Handle $handles)
    {
        $this->handles[] = $handles;
    }

    /**
     * Get handles
     *
     * @return Doctrine\Common\Collections\Collection
     */
    public function getHandles()
    {
        return $this->handles;
    }
}