53 Pa. Stat. § 49290
In all cases where a decree for the incorporation of any borough has heretofore been made by the proper court, under the general borough laws, and the petitioners have failed to record the petition for or decree of incorporation, or both, in the recorder's office of the proper county, but have otherwise complied with the law, and have been in fact organized and become a separate municipality, the said charters shall be taken and held to be legal and valid, as of the date of the decree of incorporation; and all elections held therein, and all ordinances, regulations, contracts, and other corporate acts of said boroughs, shall be taken and held as legal and valid, and of the same force and effect as if said petition for or decree of incorporation, or both, were recorded as required by law: Provided, That the petition for, or the order of incorporation of, any such borough be hereafter recorded in the proper office, nunc pro tunc.
53 P.S. § 49290