Fatal error: Call to undefined function oik_require() in oik\admin\oik-header.inc on line 2
There are two ways to fix problems like this
1. cpanel – edit or delete offending file using the website’s control panel
2. FTP – edit or delete the offending files using File Transfer Protocol
Here we use the cpanel approach to rename the offending plugin file from oik-header.php to oik-header.hph
Once the file has been removed WordPress is able to recover, giving us access to the dashboard, so that we can try again.
Use your website’s control panel to recover from an unrecoverable fatal error on WordPress admin pages. In this video we create an unrecoverable fatal error that appears when attempting to view the WordPress dashboard. The fatal error is caused by a documented bug in version 1.15 of the oik WordPress plugin.