53 Pa. Stat. § 1672
Every municipal corporation shall have power to open, widen, straighten, or extend streets or alleys, or parts thereof, within its limits, and to vacate streets or alleys, or parts thereof, upon the petition of a majority in number and interest of owners of property abutting on the line of the proposed improvements, to be verified by the affidavit of one or more parties as in the preceding section; a majority in interest of owners of undivided interests in any piece of property to be deemed and treated as one person for the purposes of petition. Every municipal corporation shall have power, whenever the councils or authorities thereof shall deem it necessary, to open, widen, straighten, or extend streets or alleys, or parts thereof, and to vacate streets or alleys, or parts thereof, without any petition of property owners. The widening or straightening ordinances shall fix the new line or lines, and may require that thereafter no owner or builder shall erect any new building or rebuild or alter the front of any building already erected without making it conform to the new lines, in which case the landowner's right of action shall accrue only when the said municipal corporation actually enters on and occupies the land within the said lines, or the said building is located or relocated to conform to said lines: Provided, The ordinance or ordinances authorizing the same shall be adopted and enacted by the affirmative vote of three-fourths of the members elect composing the councils of such municipality, and approved by the mayor, city recorder, or burgess thereof. No such ordinance shall be finally adopted and enacted in a less period than thirty (30) days from the date of its introduction, and in the meantime copies of said ordinance shall be published in each of the official newspapers of such municipality, once a week for three consecutive weeks, immediately following the introduction thereof, and, in case such municipality shall have no official newspapers, then in at least one newspaper published in the county in which the municipality is situate, once a week for three consecutive weeks.
53 P.S. § 1672