The boundaries of the various zoning districts have been indicated on the official zoning map. Such map shall be known as the "Official Zoning Map of the City of York, South Carolina" and shall be certified by the signatures of the mayor, city manager, and the members of the planning commission. The official zoning map is hereby made a part of this ordinance. All changes to the district boundaries shown on the official zoning map shall be certified by the signature of the mayor, planning commission and the city manager.