upgrade.php

<?php

/*
 * This plugin was previously known as new-members-only, and options were
 * named as new_members_only_[option_name]. If you previously had that plugin installed,
 * and you don't currently have dxw-members-only options setup, this will take the
 * new-members-only options and copy them across to the dxw_members_only format.
 */

 function transfer_new_members_only_options()
 {
     $options = [
         'list_type',
         'list_content',
         'ip_whitelist',
         'referrer_allow_list',
         'redirect',
         'redirect_root',
         'upload_default',
         'max_age',
         'max_age_static',
         'max_age_public'
     ];
     foreach ($options as $option) {
         $old_option = 'new_members_only_' . $option;
         $new_option = 'dxw_members_only_'. $option;

         //use is_null because don't want to overwrite existing but empty options
         if (!is_null(get_option($old_option, null)) && is_null(get_option($new_option, null))) {
             $old_option_val = get_option($old_option);
             add_option($new_option, $old_option_val);
         }
     }
 }