From PHP.net:

The International PHP Conference 2005 Spring Edition will take place from May 2, 2005 to May 4, 2005. The Conference features a PowerWorkshop day on May 2 with PHP/MySQL Best Practices, XML/WebServices with PHP 5, Rapid Application Development and a PHP Starter Workshop for Beginners. The main Conference days will include sessions on PHP Internals, XML, Databases, Migration to PHP 5 and others. Early bird discounts are available until April 1, 2005.

This year it's being held in the RAI Conference Center in Amsterdam (which has its own railway station and is less than ten minutes travelling time by train from Schiphol Airport). There are going to be tons of sessions choose from given by speakers such as Derick Rethans, Zeev Suraski, John Coggeshall, Sebastian Bergmann, and Ben Ramsey. Hurry and register by registering before the Early Bird deadline (April 1st) and get the special rate savings of about 100 Euro per package.