Drupal
Drupal has long prided itself for staying ahead of the curve technologically. In order to be able to write the best quality Drupal software, Drupal developers need the best programming tools available. Today, the best PHP available is PHP 5.
PHP 5 has been deployed and tested in production environments for three years. Unfortunately, web hosts have been slow to adopt PHP 5, which has made it difficult for Drupal and many other PHP projects to fully embrace PHP 5's features.
Now a growing consortium of PHP projects have joined together and push for wider PHP 5 adoption. By all embracing PHP 5 together, the projects involved in the GoPHP 5 effort are sending a message to web hosts that it is time to embrace PHP's future.
Drupal is now part of that movement.
Adoption of PHP 5.x was slow due to several reasons
1) PHP 5.x and Apache 2.0 does not work fine (there several issues and PHP team keeps on blaming Apache people, and Apache people keep on blaming PHP team and the fight is still on
2) PHP 4.x was very stable, efficient and secure.
3) PHP 5.x has JAVA style class support - which makes object oriented programming easier and faster - but people want everything to be simple and fast.
These are the precise reason for PHP 5.x being slow in adoption by hosting companies.
Vinay Yadav
PHP specialist
http://www.vinayras.com
Yes, this is planned for Drupal 7.x version.
Vinay Yadav
PHP ' Drupal specialist
http://www.vinayras.com