Results

      '#title' => $this->t('PHP contextual filter code'),
      '#default_value' => $this->options['code'],
      '#description' => $this->t('Enter PHP code that returns a value to use for this filter. Do not use <?php ?>. You must return only a single value for just this filter. Some variables are available: the view object will be "$view". The argument handler will be "$argument", for example you may change the title used for substitutions for this argument by setting "argument->validated_title".'),
    ];

    // Only do this if using one simple standard form gadget.
    $this->checkAccess($form, 'code');
  }

      '#title' => $this->t('PHP validate code'),
      '#default_value' => $this->options['code'],
      '#description' => $this->t('Enter PHP code that returns TRUE or FALSE. No return is the same as FALSE, so be SURE to return something if you do not want to declare the argument invalid. Do not use <?php ?>. The argument to validate will be "$argument" and the view will be "$view". You may change the argument by setting "$handler->argument". You may change the title used for substitutions for this argument by setting "$handler->validated_title".'),
    ];

    $this->checkAccess($form, 'code');
  }

  /**

    // Property created dynamically.
    if (!$this->argument->validated_title = $term->getName()) {
      $this->argument->validated_title = $this->t('No name');
    }

    return TRUE;
  }

}

    // Property created dynamically.
    if (!$this->argument->validated_title = $node->getName()) {
      $this->argument->validated_title = $this->t('No name');
    }

    return TRUE;
  }

}

      // Override title for substitutions.
      // @see \Drupal\views\Plugin\views\argument\ArgumentPluginBase::getTitle
      $this->argument->validated_title = $this->dateFormatter->format($time, 'custom', $this->options['replacement_format']);
      return TRUE;
    }
    return FALSE;
  }

  /**

    // Property created dynamically.
    if (!$this->argument->validated_title = $term->getName()) {
      $this->argument->validated_title = $this->t('No name');
    }

    return TRUE;
  }

}