The GMP bulds for VC8+ are based on [[http://fp.gladman.plus.com/computing/gmp4win.htm|Brian Gladman's port]]

Source code available at ftp://ftp.gnu.org/gnu/gmp/gmp-4.1.2.tar.bz2

For PHP suitable sources and up-to-date information see [[https://github.com/winlibs/mpir]].