Section 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. § 4109 (relating to child custody proceedings during military deployment), 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).Amended by P.L. 241 2012 No. 32, § 1, eff. 6/11/2012.2010, Nov. 23, P.L. 1106, No. 112, § 2, effective in 60 days [Jan. 24, 2011].