53 Pa. Stat. § 13217
No proposed charter provisions shall be submitted to the qualified electors oftener than once in every five years: Provided, however, That no petition by registered electors of the city for the appointment of a commission, as provided in subsection (a) of section 3 shall be presented to the city council of the city if the city council shall at such time already have provided, by ordinance, for the appointment of such commission, or if a petition by registered electors for the appointment of a commission shall then already have been presented to the city council, until the expiration of four years and six months next following the submission to the qualified electors of the city for their approval or disapproval of the charter provisions proposed by the commission, unless, in the case of a petition by registered electors already presented, such petition shall have been then rejected or set aside under the provisions of section 8 or section 9 of this act: And provided further, That no petition by registered electors for the appointment of a commission shall be presented to the city council until the expiration of three months next following the effective date of this act.
53 P.S. § 13217