1 module.inc module_enable($module_list, $enable_dependencies = TRUE)

Enables or installs a given list of modules.


  • "Enabling" is the process of activating a module for use by Backdrop.
  • "Disabling" is the process of deactivating a module.
  • "Installing" is the process of enabling it for the first time or after it has been uninstalled.
  • "Uninstalling" is the process of removing all traces of a module.

Order of events:

  • Gather and add module dependencies to $module_list (if applicable).
  • For each module that is being enabled:
    • Install module schema and update system registries and caches.
    • If the module is being enabled for the first time or had been uninstalled, invoke hook_install() and add it to the list of installed modules.
    • Invoke hook_enable().
  • Invoke hook_modules_installed().
  • Invoke hook_modules_enabled().


array $module_list: An array of module names.

bool $enable_dependencies: (optional)

  • If TRUE, dependency-checking is enabled. This means that any modules the passed-in module(s) depend on will be automatically added and enabled in the correct order. If any dependencies are unavailable, the passed-in module(s) will not be enabled. Note that dependency-checking incurs a significant performance cost.
  • If FALSE, dependency-checking is bypassed and the passed-in module(s) will be enabled regardless of whether or not their dependencies are available or listed in the correct order. This could lead to problems, and so should only be used if you know $module_list is already complete and in the correct order.

Return value

bool: Returns FALSE if $enable_dependencies is TRUE and one or more dependencies are missing. Otherwise returns TRUE.

See also








core/includes/module.inc, line 408
API for loading and interacting with Backdrop modules.


function module_enable($module_list, $enable_dependencies = TRUE) {
  if ($enable_dependencies) {
    // Get all module data so we can find dependencies and sort.
    $module_data = system_rebuild_module_data();
    // Create an associative array with weights as values.
    $module_list = array_flip(array_values($module_list));

    // The array is iterated over manually (instead of using a foreach) because
    // modules may be added to the list within the loop and we need to process
    // them.
    while ($module = key($module_list)) {
      if (!isset($module_data[$module])) {
        // This module is not found in the filesystem, abort.
        return FALSE;
      if ($module_data[$module]->status) {
        // Skip already enabled modules.
      $module_list[$module] = $module_data[$module]->sort;

      // Add dependencies to the list, with a placeholder weight.
      // The new modules will be processed as the while loop continues.
      foreach (array_keys($module_data[$module]->requires) as $dependency) {
        if (!isset($module_list[$dependency])) {
          $module_list[$dependency] = 0;

    if (!$module_list) {
      // Nothing to do. All modules already enabled.
      return TRUE;

    // Sort the module list by pre-calculated weights.
    $module_list = array_keys($module_list);

  // Required for module installation checks.
  include_once BACKDROP_ROOT . '/core/includes/install.inc';

  $modules_installed = array();
  $modules_enabled = array();
  foreach ($module_list as $module) {
    // Only process modules that are not already enabled.
    $existing = db_query("SELECT status FROM {system} WHERE type = :type AND name = :name", array(
      ':type' => 'module',
      ':name' => $module))
    if ($existing->status == 0) {
      // Load the module's code.
      backdrop_load('module', $module);

      // Update the database and module list to reflect the new module. This
      // needs to be done first so that the module's hook implementations,
      // hook_schema() in particular, can be called while it is being
      // installed.
        ->fields(array('status' => 1))
        ->condition('type', 'module')
        ->condition('name', $module)
      // Refresh the module list to include it.
      // Update the registry to include it.
      // Refresh the schema to include it.
      backdrop_get_schema(NULL, TRUE);
      // Update the theme registry to include it.
      // Refresh Entity info static cache.

      // Allow modules to react prior to the installation of a module.
      module_invoke_all('modules_preinstall', array($module));

      // Now install the module if necessary.
      if (backdrop_get_installed_schema_version($module, TRUE) == SCHEMA_UNINSTALLED) {

        // Set the schema version to the number of the last update provided
        // by the module.
        $versions = backdrop_get_schema_versions($module);
        $version = $versions ? end($versions) : SCHEMA_INSTALLED;

        // Copy any default configuration data to the system config directory/

        // If the module has no current updates, but has some that were
        // previously removed, set the version to the value of
        // hook_update_last_removed().
        if (empty($versions) && ($last_removed = module_invoke($module, 'update_last_removed'))) {
          $version = $last_removed;
        backdrop_set_installed_schema_version($module, $version);
        // Allow the module to perform install tasks.
        module_invoke($module, 'install');
        // Record the fact that it was installed.
        $modules_installed[] = $module;
        watchdog('system', '%module module installed.', array('%module' => $module), WATCHDOG_INFO);

      // Allow modules to react prior to the enabling of a module.
      module_invoke_all('modules_preenable', array($module));

      // Enable the module.
      module_invoke($module, 'enable');

      // Record the fact that it was enabled.
      $modules_enabled[] = $module;
      watchdog('system', '%module module enabled.', array('%module' => $module), WATCHDOG_INFO);

  // If any modules were newly installed, invoke hook_modules_installed().
  if (!empty($modules_installed)) {
    module_invoke_all('modules_installed', $modules_installed);

  // If any modules were newly enabled, invoke hook_modules_enabled().
  if (!empty($modules_enabled)) {
    module_invoke_all('modules_enabled', $modules_enabled);

  return TRUE;