53 Pa. Stat. § 10701
In order that the purposes of this act be furthered in an era of increasing urbanization and of growing demand for housing of all types and design; to insure that the provisions of Article VI which are concerned in part with the uniform treatment of dwelling type, bulk, density, intensity and open space within each zoning district, shall not be applied to the improvement of land by other than lot by lot development in a manner that would distort the objectives of that Article VI; to encourage innovations in residential and nonresidential development and renewal so that the growing demand for housing and other development may be met by greater variety in type, design and layout of dwellings and other buildings and structures and by the conservation and more efficient use of open space ancillary to said dwellings and uses; so that greater opportunities for better housing and recreation may extend to all citizens and residents of this Commonwealth; and in order to encourage a more efficient use of land and of public services and to reflect changes in the technology of land development so that economies secured may enure to the benefit of those who need homes and for other uses; and, in aid of these purposes, to provide a procedure which can relate the type, design and layout of residential and nonresidential development to the particular site and the particular demand for housing existing at the time of development in a manner consistent with the preservation of the property values within existing residential and nonresidential areas, and to insure that the increased flexibility of regulations over land development authorized herein is carried out under such administrative standards and procedures as shall encourage the disposition of proposals for land development without undue delay, the following powers are granted to all municipalities.
53 P.S. § 10701