Finding null value with get in Doctrine Entity

Hi, how are you? I'm having a problem with NULL with Doctrine . What happens: I have some fields in a database table where I save some values for future validations, these fields are nullable = true . I'll give an example: When I generate a token , I automatically generate a date for it, and when this token is used, I pass values NULL to the validateToken field, which stores the date that was generated , as well as token . To set this NULL in setter is quiet, the problem is when I search for getter getValidateToken() or getTonken() to do some checking and it is NULL in this case it tells me that I need to return a DateTime in getValidateToken() and string in getToken() and is returning NULL . Below is my code and error.

/**
 * @var string
 * @ORM\Column(type="string", length=255, nullable=true)
 */
private $token;

/**
 * @var \DateTime
 * @ORM\Column(type="datetime", nullable=true)
 */
private $validateToken;

/**
 * @return string
 */
public function getToken(): string
{
    return $this->token;
}

/**
 * @param string $token
 *
 * @return User
 */
public function setToken(string $token = null): User
{
    $this->token = $token;
    return $this;
}

/**
 * @return \DateTime
 */
public function getValidateToken(): \DateTime
{
    return $this->validateToken;
}

/**
 * @param \DateTime $validateToken
 *
 * @return User
 */
public function setValidateToken(\DateTime $validateToken = null): User
{
    $this->validateToken = $validateToken;
    return $this;
}

I know I can remove the: string and o: \ DateTime but must have a way to do it without removing.

Thanks