53 Pa. Stat. § 14133
When a city of the first class shall hereafter superimpose upon the confirmed plan of streets of said city any park or parkway, in an entirely built-up section of said city, the placing of such park or parkway on the city plan shall be considered as an appropriation to public use of the land within the lines of said park or parkway, at the expiration of five years from the date of confirmation of the plan showing such park or parkway by the board of surveyors of said city; with the same effect as if the land within the boundary of said park had been appropriated for public park purposes, or the said parkway had been opened to public use, by ordinance of councils, unless an ordinance actually appropriating said land to public use shall have been previously passed, or the ordinance placing such park or parkway on the city plan shall have been previously repealed.
53 P.S. § 14133