PHP Programming
PHP 4 has reached end of life and support for it will stop by 31 December 2007. Slowly but surely there will be a migration to PHP5. Since there is still time, it can be best utilised for preparation. It is easy to migrate to PHP 5 in a local development environment, but for migrating a live web-site, the migration is linked to the availability of PHP 5.
Official Guide to PHP 5 Migration may be seen Here