The biggest change in PHP 4.2.0 concerns variable handling. External variables (from the environment, the HTTP request, cookies or the web server) are no longer registered in the global scope by default. The preferred method of accessing these external variables is by using the new Superglobal arrays, introduced in PHP 4.1.0. More information about this change:
The Apache Software Foundation recently released their first General Availability version of Apache 2. PHP 4.2.0 will have EXPERIMENTAL support for this version. You can build a DSO module for Apache 2 with --with-apxs2. We do not recommend that you use this in a production environment.
PHP 4.2.0 still lacks certain key features on Mac OS X and Darwin, and isn't officially supported by the PHP Group on these platforms. Specifically, building PHP as a dynamically loaded Apache module isn't supported at this time. PHP 4.3.0, due to be released in August, 2002, will be the first PHP release to officially support Mac OS X. It, along with future Mac OS X and Apache releases, will enable full feature parity with other PHP platforms. Update: Instructions on overcoming these limitations
PHP 4.2.0 includes several improvements:
For a full list of changes in PHP 4.2.0, see the ChangeLog.