update_module_enable_example.php

<?php

function example_update_N(){
  // This manually enables the module using the same function features will use in the other example
  features_module_enable('backup_migrate');
  
  // Now you don't need to revert dependencies component because you've already enabled the module that you added.
  $features['site_config'] = array('variable');
  $features_rebuild($features);
  $features_revert($features);
}

function example_update_N(){
  // By reverting the dependencies component, you tell features to run features_module_enable() on any 
  // dependencies which are missing. Ta da!
  $features['site_config'] = array('variable', 'dependencies');
  $features_rebuild($features);
  $features_revert($features);
}

?>