Since grid computing (that's what I'm currently doing) also is very much about Single-sign on and delegation of rights, username/password authentication schemes don't quite do it for us. Thus, a PKI (public key infrastructure) based on X.509 is employed.

He explains the acronym soup by defining the process as advanced means of "showing the web who you are". He explains some of the basics about the certificates and who good candidates for this type of authentication are. Then the tech starts - how to get Apache configured to use them and how to use them in PHP to authenticate the external user (requiring OpenSSL compiled in to access the needed functions).

Short list of what you can find there: Namespaces, __callstatic() magic method, accessing static members through $foo::myFunc(), fully rewritten ini-parser with .htaccess-like user defined ini files for CGI/FastCGI, improved OpenSSL extension, PCRE 7.4, and other fixes and improvements that will never get into 5_2 branch.

He recommends teching throughly before the major release to find all of the bug before the general public does. Builds for both source and Windows systems have been posted.