PHP Notice: 'Array to string conversion' while making symfony form template
<p>I'm following <a href="http://symfony.com/doc/current/book/forms.html" rel="nofollow">A symfony tutorial in the official documentation</a>.
However When I get to <a href="http://symfony.com/doc/current/book/forms.html#field-type-options" rel="nofollow">Field Type Options</a> symfony throws the error
"An exception has been thrown during the rendering of a template ("Notice: Array to string conversion") in form_div_layout.html.twig at line 13."</p>

<p>I have checked on google and typos, the offending line, from the documentation seems to be: </p>

<pre><code>-&gt;add('dueDate', DateType::class, array('widget' =&gt; 'single_text'))
</code></pre>

<p>Which is straight from the documentation.
For context the rest of the file looks like this:</p>

<pre><code>&lt;?php

namespace AppBundle\Controller;

use AppBundle\Entity\Task;

use Symfony\Component\Form\Extension\Core\Type\TextType;
use Symfony\Component\Form\Extension\Core\Type\DateType;
use Symfony\Component\Form\Extension\Core\Type\SubmitType;

use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Symfony\Component\HttpFoundation\Request;

class DefaultController extends Controller
{
    /**
     * @Route("/", name="homepage")
     */
    public function indexAction(Request $request)
    {
        // replace this example code with whatever you need
        return $this-&gt;render('default/index.html.twig', [
            'base_dir' =&gt; realpath($this-&gt;getParameter('kernel.root_dir').'/..'),
        ]);
    }

    /**
     * @Route("/form", name="formmma")
     */
    public function newAction(Request $request)
    {
        // create a task and give it some dummy data for this example
        $task = new Task();
        $task-&gt;setTask('Write a blog post');

        $task-&gt;setDueDate(new \DateTime('tomorrow'));

        $form = $this-&gt;createFormBuilder($task)
            -&gt;add('task', TextType::class)
           // -&gt;add('dueDate', DateType::class)
            -&gt;add('dueDate', DateType::class, array('widget' =&gt; 'single_text'))
           // -&gt;add('dueDate', null, array(
           //     'widget' =&gt; 'single_text',
           //     'required' =&gt; false
           // ))

            -&gt;add('save', SubmitType::class, array('label' =&gt; 'Create Task'))
            -&gt;getForm();

        $form-&gt;handleRequest($request);

        if ($form-&gt;isSubmitted() &amp;&amp; $form-&gt;isValid()) {
             // ... perform some action, such as saving the task to the database

             return $this-&gt;redirectToRoute('task_success');
        }

        return $this-&gt;render('default/new.html.twig', array(
            'form' =&gt; $form-&gt;createView(),
        ));
    }
}
</code></pre>