Creating Custom Modules tutorial doesn't work - help! I'm trying to teach myself how to create a custom module using Drupal 8, and followed the instructions on their website at this Drupal.org documentation page

I created the folders, hello_world.info.yml, hello_world.routing.yml and HelloController.php pages and have been over them time and time again looking for typos, but can't find any.

I've got to the step to add add a routing file.  The module appears in the Extend area, but when I enable it and click Install, after a short pause I get the error "The website encountered an unexpected error. Please try again later."

When I go back to thet Extend, the module is ticked and I presume installed.

However when I then try to display it using the URL "/hello", I get a "Page Not Found".  Not only that, but every time I try to clear the cache, there is a delay and I get the same "Website encountered..." error again.  I can only clear the cache by uninstalling the module.

I've included the content of the three files below:

/modules/hello_world/hello_world.info.yml

name: Hello world Module
description: Creates a page showing "Hello world"
package: Custom
type: module
core: 8.x


/modules/hello_world/hello_world.routing.yml

hello_world.content:
  path: '/hello'
  defaults:
    _controller: '\Drupal\hello_world\Controller\HelloController::content'
    _title: 'Hello world'
  requirements:
    _permission: 'access content'


/modules/hello_world/src/Controller/HelloController.php

&lt;?php
    namespace Drupal\hello_world\Controller;

    use Drupal\Core\Controller\ControllerBase;

    class HelloController extendes ControllerBase {

        public function content() {
            return array(
                '#type' =&gt; 'markup',
                '#markup' =&gt; $this-&gt;t('Hello World'),
            );
        }
    }


Does anyone have any suggestions what might be wrong?
class HelloController extendes ControllerBase {


You spelled extends incorrectly.