Extra compensation not to be granted public officer, employee, contractor, etc., after service rendered or contract made; increase or decrease of compensation of officers during term of office.

The legislature shall have no power to grant or to authorize or require any county or municipal authority to grant, nor shall any county or municipal authority have power to grant any extra compensation, fee, or allowance to any public officer, servant, or employe, agent or contractor, after service shall have been rendered or contract made, nor to increase or decrease the fees and compensation of such officers during their terms of office; nor shall any officer of the state bind the state to the payment of any sum of money but by authority of law; provided this section shall not apply to allowances made by commissioners' courts or boards of revenue to county officers for ex officio services, nor prevent the legislature from increasing or diminishing at any time the allowance to sheriffs or other officers for feeding, transferring, or guarding prisoners.