53 Pa. Stat. § 22630
Every contract involving an appropriation of money shall designate the item of appropriation on which it is founded, and shall be numbered by the controller in the order of its date, and charged as numbered against such item, and so certified by him, before it shall take effect as a contract, and shall not be payable out of any other fund; and if he shall certify any contract in excess of the appropriation properly applicable thereto, the city shall not be liable for such excess, but the controller and his sureties shall be liable in damages for an amount not exceeding such excess, which may be recovered in an action on the case for negligence by the contracting party aggrieved: Provided, That so much of this section that enacts that a contract, certified by the controller, shall not be payable out of any other fund than the item of appropriation against which it is numbered, shall not apply to such contracts for public improvement as are referred to in Article XV, Section 1, hereof.
53 P.S. § 22630