PHP 5.3.0-alpha1 introduces some changes for windows users. These result in a faster, more secure binary but do not affect the way PHP works.

The PHP 5.3.0 branch will only support Windows 2000, XP, Server 2003, Vista, and Server 2008. Support has been dropped for Windows 98, ME, and NT.

Many dependent libraries have been updated to their latest versions, which means new features (up to the latest available in the unix world), bugfixes and security fixes.

The VC6 compiler used for building PHP was originally released in 1998 - that makes it 10 years old and very poor in standards support. Because of this 5.3 will have two builds for PHP, one built with VC6 and a second built with a newer compiler. If you are using third party extensions or the Apache webserver, you will need to continue using the VC6 version until Apache or your third party extension provides VC9 versions of their software.

NOTICE: the PHP 5.3 branch (that means all 5.3.x releases) will be the last releases to support VC6 Future versions of PHP will be compiled only on VC9

New builds are built with VC9 (Microsoft Visual C++ 2008). This requires a new C runtime (msvcr90.dll) which is available from microsoft. An msi installer for the runtime will be included in the .zip files for the VC9 Binaries, you only need to install it once. The complete PHP .msi installer will take care of this automatically for you.

64 bit binaries will now be distributed. These are “experimental” builds and not recommended for production use. Please report issues.

Starting with 5.3, PECL extensions will not be included with PHP, instead they will be available from the PECL site. Until the new PECL build system is working, PECL extensions will be unavailable.

Binary releases will be (to the best of our ability) synced with PHP source releases, instead of having a day or two lag between the source and windows binaries.