How to disable/enable keys

Try this if you didn't solved yours issue yet

Code:

$config = array(
array(
'field' => 'length', // this must match yours <input name=""> field in form
'label' => 'Length',
'rules' => 'required|regex_match/[0-9.]/', // you had extra ' on end
'errors' => array( 'required' => 'Provide%s', '%sNumbersOnly' )
)
); // you didn't closed array here

I get this error message. Unable to access an error message corresponding to your field name Length.(regex_match/)

Update

Ive been thinking my problem maybe the version Im operating - const CI_VERSION = '3.1.9';

I cant find anything in the manual about regex_match so guess its in v4