53 Pa. Stat. § 3231
Wherever any park or parkway may hereafter be superimposed upon the confirmed plan of the streets or parks of any city of this Commonwealth, in sections not entirely built up, by ordinance of councils or by appropriate action of the park commissioners thereof, unless an ordinance actually appropriating the land within the lines of said park or parkway to public use be duly passed by councils thereof, or said land be acquired by the park commissioners, in accordance with existing laws, within three years from the passage of said ordinance or action of the park commissioners superimposing said plan upon said land, said ordinance or action of the park commissioners superimposing said plans upon said land shall be void and of no effect in regard to said land, and said plan shall be automatically removed from said land as if it had never been placed thereon, nor shall any plan again be superimposed on said land without an accompanying ordinance condemning same to public use.
53 P.S. § 3231