53 Pa. Stat. § 13116
No proposal of a new charter or amendments of similar substance, purpose and intent 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, either for the appointment of a charter commission or proposing amendments to a charter, as provided in subsection (a) of section two and section six of this act, 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 a charter commission, or if a petition by registered electors for the appointment of a charter 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 proposed by the charter 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 seven or section eight of this act: And provided further, That no petition by registered electors for the appointment of a charter 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. § 13116