Symfony2: Could not load type "submit" - forms

Question

I am working with Symfony building a form in a Controller. Upon trying to view to the form on my browser; I get the following error page which states: "Could not load type "submit"". Whilst there are similar questions to this one, none address the submit button. In this instance what is the best way of solving this problem?
This is my controller(below)
public function indexAction(Request $request)
{
$user = new User();
$user->setFirstname("isambard");
$user->setEmail("wewewewew#hotmail.co.uk");
$user->setEnquiry("asdasda");
$form = $this->createFormBuilder($user)
->add('firstname','text')
->add('email', 'text')
->add('save','submit', array('label' => 'Create Task'))
->getForm();
return $this->render('delete.html.twig', array(
'form' => $form->createView(),
));
}
This is my User entity class (below):
class User
{
/**
* #var integer
*
* #ORM\Column(name="id", type="integer")
* #ORM\Id
* #ORM\GeneratedValue(strategy="AUTO")
*/
private $id;
/**
* #var string
*
* #ORM\Column(name="firstname", type="string", length=100)
*/
private $firstname;
/**
* #var string
*
* #ORM\Column(name="email", type="string", length=100)
*/
private $email;
/**
* #var string
*
* #ORM\Column(name="enquiry", type="string", length=100)
*/
private $enquiry;
/**
* Get id
*
* #return integer
*/
public function getId()
{
return $this->id;
}
/**
* Set firstname
*
* #param string $firstname
* #return User
*/
public function setFirstname($firstname)
{
$this->firstname = $firstname;
return $this;
}
/**
* Get firstname
*
* #return string
*/
public function getFirstname()
{
return $this->firstname;
}
/**
* Set email
*
* #param string $email
* #return User
*/
public function setEmail($email)
{
$this->email = $email;
return $this;
}
/**
* Get email
*
* #return string
*/
public function getEmail()
{
return $this->email;
}
/**
* Set enquiry
*
* #param string $enquiry
* #return User
*/
public function setEnquiry($enquiry)
{
$this->enquiry = $enquiry;
return $this;
}
/**
* Get enquiry
*
* #return string
*/
public function getEnquiry()
{
return $this->enquiry;
}
}

Answer 1

This is probably because you are using an older version of Symfony framework. As the documentation states.
2.3 Support for submit buttons was introduced in Symfony 2.3. Before that, you had to add buttons to the form's HTML manually.
You should either update your framework or manually insert the submit button in the twig template.