53 Pa. Stat. § 30651
An additional executive department in the government of cities of the second class is hereby created, to be known as the Department of City Planning, which shall be in charge of a City Planning Commission, consisting of nine persons, who may or may not be residents of the city, at least seven of whom shall not be paid city employés, to be appointed by the mayor; three of them shall be designated to serve two years from January first, one thousand nine hundred twenty-two; and three, four years therefrom; and three, six years therefrom. Their successors shall be appointed, on the expiration of their respective terms, to serve six years. An appointment to fill a casual vacancy shall be only for the unexpired portion of the term. Three shall be a quorum. They may make and alter rules and regulations for their own organization and procedure, consistent with the ordinance of the city and the laws of the Commonwealth. They shall serve without compensation, and make, annually, to the mayor, a report of their transactions and recommendations. They may employ engineers and other persons, whose salaries and wages, and other necessary expenses of the commission, shall be provided for, in the discretion of councils, by the proper appropriations and ordinances.
53 P.S. § 30651