"I guess you could say [PHP 6] was too ambitious," said Zeev Suraski, one of the principal contributors to PHP as well as the chief technology officer and co-founder of PHP software vendor Zend Technologies.
While the use of more memory may not be a big deal for a server running a single Web site, many of PHP's users run large sites requiring multiple servers operating at full capacity. "When you have a popular website, it's all about density: how many requests per second can your server take?" Suraski said. For these users, a greater memory requirement would translate directly into the need to buy more servers.
Because of this excess memory usage, the developers have temporarily halted work on the PHP 6.0 project, focusing their efforts instead on PHP 5.4 instead.
At first glance, the idea to move to Unicode makes sense for PHP. It is the most widely used server-side scripting language around the world, according to an ongoing survey from Q-Success's W3Techs. Rasmus Lerdorf created PHP in 1995 to help creating dynamic Web pages by providing basic programming concepts to augment the static markup offered by HTML. PHP is an abbreviation of PHP: Hypertext Preprocessor, a recursive algorithm.
Building a Unicode-based PHP, however, developers found their implementation required twice the run-time memory. Perhaps this is not surprising given that many of the characters in Unicode require multiple bytes to render. As a result, the software, though operational, was "significantly slower," Suraski said.
One new project is called Traits, which will allow a developer to use a specific piece of functionality in multiple parts of an application. "In each class where you wanted to support logging, you could just use the logging Trait," Suraski said. Suraski likened Traits to Java's Multiple Inheritance.
Also, many of the features that have been deprecated from PHP and were set to be removed in version 6.0 are now being removed in 5.4 instead. One example of this is PHP's Safe Mode, a mode of operation designed for running PHP in multisite implementations. Safe Mode has been both notoriously buggy and gave users a "false sense of security," Suraski said.