Read only input fields not working?

I'm trying to make an input field readonly in grocery crud enterprise;

$crud->fieldType('user_name', 'readonly');
$crud->fieldType('user_tel', 'readonly');
$crud->fieldType('start_date', 'readonly');

I've tried the above method but it just doesn't seem to work. It just lists the input field as normal, fully editable.

$crud->readOnlyFields(['user_name', 'user_tel', 'start_date']);

I've also tried using this method.. which kind of works? By the looks of it it certainly does make the fields read only. But for some reason the field values aren't being posted when I submit the form.

Am I missing something?

Read only input fields not working?

ChrisCross