53 Pa. Stat. § 59110
Hereafter no township of the first class, nor any part of any such township, shall be annexed to a contiguous city or borough in accordance with any existing law providing for such annexation, unless the voters of the entire township have first consented to such annexation. Whenever any proceeding for such annexation shall be commenced, the same shall not be concluded and the annexation shall not become effective until there has first been submitted to the electors of the entire township, in accordance with the election law for the submission of such questions, a proper question to ascertain the will of the electors with respect to such proposed annexation. Such question shall be printed on ballots provided by the county commissioners, and shall be submitted at any general or municipal election occurring at least sixty days after a petition shall have been filed with the county commissioners, by the corporate authorities of the borough or city to which such annexation is to be made, asking for the submission of such question. If at any such election, a majority of those voting on such question shall consent to such annexation, then such annexation may be made and concluded in the manner provided by law; but if a majority of those voting on the question shall vote against such annexation, then no further proceedings for such annexation shall be had. Any such question shall not be submitted oftener than once in five years. Nothing contained in this act shall be construed to apply to proceedings under existing law where provision is now or hereafter made to secure the consent of the electors of any township to any such annexation.
53 P.S. § 59110