If the petition accompanying the proposed ordinance is signed by electors of the city as required in section 11033(a)(2) (relating to number of signatures, examination and certificate by city clerk), council shall do one of the following:
(1) Enact the proposed ordinance without alteration within 20 days, except as otherwise provided in this chapter, after attachment of the city clerk's certificate to the accompanying petition.
(2) Call for a referendum to be held at the time of the next general, municipal or primary election occurring at least 90 days thereafter, at which election the proposed ordinance must be submitted, without alteration, to the electors of the city for a vote, after attachment of the city clerk's certificate to the accompanying petition. Notice of the election and the text of the question to be submitted to the electors shall be published in the same manner as publication is required in section 1201 of the Pennsylvania Election Code.