23 Pa.C.S. § 5338: Modification of existing order.

(a) Best interest of the child.--Upon petition, a court may modify a custody order to serve the best interest of the child.

(b) Applicability.--Except as provided in 51 Pa.C.S. Ch. 46 (relating to uniform deployed parents custody and visitation), this section shall apply to any custody order entered by a court of this Commonwealth or any other state subject to the jurisdictional requirements set forth in Chapter 54 (relating to uniform child custody jurisdiction and enforcement).