53 Pa. Stat. § 12521
From and after the first Monday of January, one thousand nine hundred and twenty, the legislative branch of the government of each city of the first class shall consist of a city council elected as hereinafter provided. Such council shall have and exercise all the legislative power of such city and all powers and duties theretofore had and exercised by the previously existing legislative branch of government in such city, whether the same were had and exercised by a single chamber, or by two chambers acting jointly or concurrently, or by either of them acting separately. It is the intention of this act that the council herein provided for shall take the place of the council or councils existing in any city of the first class at the date aforesaid or in any city when it may hereafter become a city of the first class, but that the powers, duties, and functions of the legislative branch of the city government shall continue unchanged except as herein provided or as may be hereafter provided by law. The mayor and heads of executive departments of any such city shall have the right at all times to appear before the council, or any committee thereof, for the purpose of expressing their views on matters pending before said council or committee.
53 P.S. § 12521