In William Penn Parking Garage, Inc. v. City of Pittsburgh, 464 Pa. 168, 346 A.2d 269 (1975), the Supreme Court held that a party has standing to sue if he or she has a "substantial, direct, and immediate interest" in the subject matter of the litigation. Id. at 192, 346 A.2d at 281. In William Penn, residents, taxpayers and operators of parking lots were affected by a tax ordinance that imposed a tax on patrons of non-residential parking places. The plaintiffs challenged the ordinance and were held to have standing because they were aggrieved by the ordinance. In other words, those challenging the taxing ordinances in that case were parking lot taxpayers and were able to bring their action for that reason because they showed a substantial, direct and immediate interest in the imposition of the tax. Guided by much of our Supreme Court's discussion in William Penn, cases that followed elaborated on the substantial-direct-immediate test. The elements have been defined as follows: A "substantial" interest is an interest in the outcome of the litigation which surpasses the common interest of all citizens in procuring obedience to the law. ... A "direct" interest requires a showing that the matter complained of caused harm to the party's interest. ... An "immediate" interest involves the nature of the causal connection between the action complained of and the injury to the party challenging it, ... and is shown where the interest the party seeks to protect is within the zone of interests sought to be protected by the statute or constitutional guarantee in question. South Whitehall Township Police Service v. South Whitehall Township, 521 Pa. 82, 86-87, 555 A.2d 793, 795 (1989).