PHP.net has formally announced today that PHP4.x will no longer will supported from 31st December 2007 as PHP 5.0 is stable for production and they are well on their way to PHP 6. Read below:
PHP 4 end of life announcement
Today it is exactly three years ago since PHP 5 has been released. In those three years it has seen many improvements over PHP 4. PHP 5 is fast, stable & production-ready and as PHP 6 is on the way, PHP 4 will be discontinued.
The PHP development team hereby announces that support for PHP 4 will continue until the end of this year only. After 2007-12-31 there will be no more releases of PHP 4.4. We will continue to make critical security fixes available on a case-by-case basis until 2008-08-08. Please use the rest of this year to make your application suitable to run on PHP 5.
For documentation on migration for PHP 4 to PHP 5, we would like to point you to our migration guide. There is additional information available in the PHP 5.0 to PHP 5.1 and PHP 5.1 to PHP 5.2 migration guides as well.
For those of you who are still using 4.x, it means that it is high time to upgrade to PHP 5.