Overriding Drupal 8 Configuration Values in settings.php

In previous versions of Drupal you would see values from settings.php on the coniguration pages. For instance $conf['mymodule_setting_value'] = 'My Value'; would display "My Value" in the text field and whenever you would try make a change to the field and try hit save button the value of the field would reset to the value specified in settings.php . However in Drupal 8 overridinen configuration form values in settings won't reflect in the form.

There is an issue on Drupal.org for that and developers already found a solution and it should be fixed in Drupal core soon.

Below I am going to provide an example of a simple config form value override in settings.php .

Drupal 8 configuraiton form example:

/**
 * @file
 * Contains \Drupal\mymodule\Form\BasicSettingsForm.
 */

namespace Drupal\mymodule\Form;

use Drupal\Core\Form\ConfigFormBase;
use Drupal\Core\Form\FormStateInterface;

/**
 * Form builder for the mymodule basic settings form.
 */
class BasicSettingsForm extends ConfigFormBase {

  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'mymodule_basic_settings_form';
  }

  /**
   * {@inheritdoc}
   */
  protected function getEditableConfigNames() {
    return ['mymodule.settings'];
  }

  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) {
    $config = $this->config('mymodule.settings');

    $form['text_val'] = [
      '#type' => 'textfield',
      '#title' => $this->t('My Module setting'),
      '#default_value' => $config->get('text_val'),
    ];

    $form['group_setting1'] = [
      '#type' => 'textfield',
      '#title' => $this->t('Setting 1'),
      '#default_value' => $config->get('group.setting1'),
    ];

    $form['group_setting2'] = [
      '#type' => 'textfield',
      '#title' => $this->t('Setting 2'),
      '#default_value' => $config->get('group.setting2'),
    ];

    return parent::buildForm($form, $form_state);
  }

  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    parent::submitForm($form, $form_state);
    $config = $this->config('mymodule.settings');
    $config->set('text_val', $form_state->getValue('text_val'));
    $config->set('group.setting1', $form_state->getValue('group_setting1'));
    $config->set('group.setting2', $form_state->getValue('group_setting2'));
    $config->save();
  }

}

To override configuration values use the following format in settings.php :

$config['mymodule.settings'] = [
  // Simple text value override.
  'text_val' => 'Value from settings.php',
  // Groupped values.
  'group' => [
    'setting1'   => 'Value 1',
    'setting2'   => 'Value 2',
  ],
];

You could also use drush to see the values of your configuration forms by using the following command:

drush cget mymodule.settings 

$settings variable

You could also use $settings in settings.php to control your module settings or any other conditional logic.

Add the following to settings.php

$settings['my_setting'] = 'My Setting Value';

And this is how you would access the variable in your code:

use Drupal\Core\Site\Settings;

function my_function() {
  $mySetting = Settings::get('my_setting', NULL);
}