FOS\UserBundle\Model\User::addRole PHP Method

    public function addRole($role)
    {
        $role = strtoupper($role);
        if ($role === self::ROLE_DEFAULT) {
            return;
        }
        if (!in_array($role, $this->roles, true)) {
            $this->roles[] = $role;
        }
    }

 public function addRole($role)
 {
     if (is_string($role)) {
         return parent::addRole($role);
     } elseif ($role instanceof Role) {
         return parent::addRole($role->getRole());
     } else {
         throw new \InvalidArgumentException("Role must be a string or Role symfony object");
     }
 }