The council shall provide by ordinance for the exercise of a control function, in the management of the finances of the city, by the city controller. The control function shall include provision for an encumbrance system of budget operation, for expenditures only upon written requisition, for the pre-audit by the city controller of all claims and demands against the city prior to payment, and for the control of all payments out of any public funds by individual warrants for each payment to the official having custody thereof.
53 P.S. § 41420