Twig

PHP Class using StringTranslationTrait

StringTranslationTrait allow to get t() and formatPlural() methods
Example:
use Drupal\Core\StringTranslation\StringTranslationTrait;
use Drupal\Core\StringTranslation\TranslationInterface;
class MyClass {


Example 1. Basic inline template

    $output[] = [
      '#type' => 'inline_template',
      '#template' => '{{ yourvar }}',
      '#context' => [
        'yourvar' => 'The Value',
      ],
    ];
    return $output;

Example 1, with FieldPluginBase (\Drupal\views\Plugin\views\field\FieldPluginBase)

Step 1. Create your module and Block (/tutoriels/107/create-a-simple-block-programmatically)

Step 2. Add your template usin hook_theme()  (here module name = clock)

Enable debugging

You enable Twig Debugging in sites/default/services.yml.
(If services.yml does not yet exist; copy default.services.yml and rename it to services.yml.)

parameters:
 twig.config:
  debug: true

Printing variables

Print : {{ variable_to_print }}
Code : {% codes %}
Comment : {# Comments #}
 

Official guides:

https://www.drupal.org/theme-guide/8/twig
https://www.drupal.org/theme-guide/8