PHP 4 is Dead�Long Live PHP 5

PHP 4, deployed on tens of millions of servers globally, is among the most successful languages of all time. But its run is coming to an end.

Active development for the scripting language has been discontinued and security updates will conclude in August. And for some developers, PHP 4 will be history before Valentine's Day.

On February 5, a group of influential Open Source projects will collectively stop all new development on their respectively platforms using PHP 4.

However, there are still some holdouts opposing a complete transition to PHP 5 and it's not entirely clear whether or not PHP 4 will ever truly disappear.

PHP 5 isn't a new technology, either. But it's been the anointed successor to PHP 4 since PHP 5's initial launch in 2004.

"We're confident in PHP 5," Andi Gutmans, CTO of Zend, PHP's lead commercial backer, told InternetNews.com. "We don't believe you can go to the modern web with AJAX, XML and Web Services with PHP 4, which is why we're definitely backing PHP 5 very strongly."

PHP 5 includes many Web 2.0 optimizations that improve performance, management and scalability of XML, Web Services and other key Web 2.0 technologies.

In Gutmans' view, there actually isn't a large PHP 4 user base out in the market today. However, there is a huge install base for PHP 4 applications.

"Almost all of our customers are doing development in PHP 5," Gutmans said. "But obviously there is a huge installed based out there. If it works and you don't have to do development on it, there is no reason to switch versions."

The deeper issue though is the fact that until February 5, there are still a large number of open source projects that still develop their applications with support for PHP 4. So far, projects running PHP 4 on their servers have not been driven to migrate to PHP 5.

With its February 5 deadline for PHP switchover, The GoPHP5.org effort is hoping to change that paradigm.

Robert Douglass co-author of Building Online Communities With Drupal, phpBB, and WordPress and longtime contributor to the open source Drupal project is helping to lead the GoPHP5.org effort.

Douglass told InternetNews.com that Drupal has always been a fast, leading-edge project but, in his view, the continued need to support PHP 4 has held it back.

And simply dumping PHP 4, won't necessarily solve all of the project's problems. Drupal has the goal of being an easily installable package that could be installed on a wide variety of hosts.

The chicken or the egg?

"There was a Catch-22," Douglass explained. "Hosts didn't seem to be driving toward adopting PHP 5, yet we wanted to move on to this new era of PHP development and we strongly felt that the hosts were holding us back."

When Drupal looked at the problem a little closer, they realized that it wasn't just the hosts who were at fault but also the software providers because the majority provide software that is PHP 4 compatible.

"We realized there was a chicken and egg problem," Douglass said. "The hosts didn't want to upgrade to PHP 5 until there was a critical mass of people using it. And for developers they didn't want to use PHP 5 until it was something that was a viable option for deployment with hosts."

That's why GoPHP5.org was created—to get software developers together to collectively decide when it was time to move development to PHP 5.

While the group is pushing for PHP 5 adoption, it's not asking developers to abandon their existing PHP 4 users.

"We didn't expect any project to break software or say that people who want to stay with PHP 4 for older versions are out of luck," Douglass said. "Every project has it for themselves to decide when they want to stop supporting PHP 4 with existing versions of their software."

Moving from PHP 4 to PHP 5 isn't as easy as just flipping a switch or ticking a tick box on a development environment.

Douglass admitted there are several "generally known snafus and gotchas" that can complicate matters when moving from one version of PHP to the other. In his view, most of those issues aren't critical but some applications could have fatal errors and break.

That's where focused PHP 5 development comes in.

There are also those who oppose the GoPHP5.org effort, including the predictably named StopPHP5.org effort.

On its Web site, StopPHP5.org claims that it will even pay hosts to stick with PHP 4. StopPHP5.org officials were not immediately available for comment.

Douglass considers the StopPHP5.org site to be a spoof site and a form of flattery. While Douglass and his cohorts at GoPHP5 are all about moving to PHP 5, Douglass admitted that PHP 4 is likely to stick around for a long time.

"I would expect PHP 4 use to taper off with new projects primarily launched in PHP 5," Douglass said. "Some projects will run on PHP 4 indefinitely. I wouldn't be surprised if in 50 years you would still find PHP 4. It does its job well and has had an enormous role in building the Internet."