No claim against the city shall be paid, unless it is evidenced by a purchase order approved by the head of the department or office for which the indebtedness was incurred; and each director or officer and his surety shall be liable to the city for all loss or damage sustained by the city by reason of his negligent or corrupt approval of any such claim. The controller of accounts shall examine all payrolls, bills and other claims and demands against the city, and shall issue no warrant for payment unless he finds that the claim is in proper form, correctly computed and duly approved; that it is justly and legally due and payable; that an appropriation has been made therefor which has not been exhausted, or that the payment has been otherwise legally authorized; and that there is money in the city treasury to make payment. He may investigate any claim and for that purpose may summon before him any officer, agent or person, and examine him upon oath or affirmation relative thereto, which oath or affirmation he may administer. If the controller of accounts issues a warrant on the treasury authorizing payment of any item for which no appropriation has been made, or for the payment of which there is not a sufficient balance in the proper appropriation, or which is otherwise contrary to law or ordinance, he and his sureties shall be individually liable to the city for the amount thereof.