How do I disable a single option from select I have used a taxonomy entity reference to fill the values of a select form field. Based on the user roles, I want to limit the options between Submitted, Reviewed, Accepted, and Rejected.

I have used a content type to submit ideas. The field idea status is disabled for a subscriber role and available for moderator role and approver role. I want the Moderator to get the status Reviewed and Rejected. Approver should see Accepted and Rejected status.

How can I achieve this?
The options can be hidden by a one liner code,

unset($form['field_name']['und']['#options'][1]);


where 

['field_name'] is the name of the your field

[1] is the index of the option in the list

In my case [1] is Submitted, [2] is Reviewed, [3] is Accepted and [4] is Rejected