PHP 6

PHP 6 was an ambitious but ultimately canceled version of the PHP programming language. It aimed to solve major problems, especially related to Unicode support. Despite years of development, the project did not reach a stable release. Many of its ideas were later folded into PHP 5.3 and PHP 7. The version number PHP 6 became associated with failure in the PHP community and was skipped when the next major version was released.

Background and Development Goals

In the early 2000s, PHP had become one of the most used server-side scripting languages on the web. However, it lacked full Unicode support, which limited its usefulness in global applications. As the internet expanded, handling multiple languages and writing systems became more important.

PHP 6 development started in 2005. The primary goal was native Unicode support throughout the language. This meant changing how strings worked, rewriting the engine to handle multibyte characters, and updating many functions. Internally, PHP strings were to use UTF-16 encoding, which would allow better handling of international text.

Alongside Unicode support, PHP 6 aimed to modernize the language in other ways, including:

• Adding contemporary programming features
• Improving overall performance
• Cleaning up outdated or inconsistent parts of the core

Despite the ambitious plans, PHP 6 struggled with technical complexity—especially around Unicode implementation—and was eventually abandoned.

Main Features Planned for PHP 6

• Native Unicode Support - The core goal of PHP 6 was native Unicode handling. It aimed to store all strings as Unicode internally. Developers could then process multilingual data without relying on external libraries or conversion steps. This change required deep changes in the Zend Engine and affected string functions, input/output handling, and memory use.
• Improved Type Hinting - PHP 6 aimed to strengthen the language’s typing system. It would allow more control over function inputs and outputs by specifying expected types, helping developers catch errors earlier.
• Cleaner Syntax - The plan included removing deprecated features and syntax inconsistencies. Some legacy features from earlier PHP versions would be removed or replaced.
• Namespaces - Namespaces were a frequently requested feature in PHP. They allow better organization of code and avoid class name conflicts in large projects. Though part of the PHP 6 plan, namespaces were eventually added in PHP 5.3.
• Improved Object-Oriented Features - Object-oriented programming was still being fully adopted by many PHP developers at the time. PHP 6 intended to strengthen class support and provide better tools for working with objects.

Problems and Project Failure

The PHP 6 project faced technical and organizational problems.

• Unicode Complexity - Adding full Unicode support required rewriting core parts of the language. This task proved far more complex than expected. Many existing PHP functions operated on byte-level strings and could not easily adapt to UTF-16. Memory usage increased, performance dropped, and compatibility with extensions broke. Maintaining Unicode internally would also have created confusion between Unicode strings and binary strings. Developers needed to understand both cases and manage encoding in their code.
• Fragmented Development - The PHP development community had disagreements about how to implement Unicode. There were different views on whether to use UTF-8 or UTF-16, what to do with backward compatibility, and how much of the language to rewrite. These disagreements slowed progress.
• Lack of Working Code - After years of development, the PHP 6 codebase was large but incomplete. Many features were unfinished or buggy. No stable version was ever released. Developers could download experimental builds, but they were not ready for production use.
• Resource Drain - The focus on Unicode drew attention away from other features. As the PHP 6 project stalled, useful improvements could not reach users. This led to growing frustration in the PHP community.

What Happened to PHP 6

By 2010, it was clear that PHP 6 had failed. The Unicode changes were too difficult to finish. Developers decided to abandon the project and move useful features into other releases.

Several planned features from PHP 6 were included in PHP 5.3, released in 2009. These included:

• Namespaces
• Late static binding
• Nowdoc syntax
• Improved object support

Other changes that had been delayed by PHP 6 were added in PHP 5.4 and later.

Because the name “PHP 6” had become linked to a failed project, the next major version was called PHP 7. This skipped versioning helped signal a clean break from the old plans.

Differences Between PHP 6 and PHP 7

PHP 7, released in 2015, shared some goals with PHP 6. It aimed for better performance, improved type safety, and modern syntax. However, it did not include full Unicode support. PHP 7 took a more cautious path. Instead of rewriting string handling, it optimized the language for speed and efficiency.

The key differences between the abandoned PHP 6 and released PHP 7 include:

Lasting Impact

PHP 6 is remembered as a turning point in the history of PHP. Though it failed as a release, it taught developers several lessons:

• Large rewrites must be carefully planned.
• Compatibility matters in mature languages.
• Community coordination is key in open-source projects.

Many of the original PHP 6 ideas were later rethought and included in a more practical form. The process of failure helped the language grow stronger.

The experience also showed that not every technical goal fits well with how a language is used. For PHP, which often runs on shared servers with limited control, performance and compatibility were more important than deep internal changes.

Advantages That Were Expected

Though PHP 6 never launched, the planned features would have provided several benefits if completed:

• Native Unicode would have allowed PHP to better serve global applications.
• Cleaner syntax would have made the code easier to read and maintain.
• Improved type safety could have reduced bugs in large systems.
• Object-oriented tools would have supported better software design.

Instead, many of these advantages arrived over time in smaller steps through later versions.

Why the Version Number Was Skipped

Skipping PHP 6 was not only symbolic. It helped prevent confusion. By the time PHP 7 was in development, books, articles, and documentation already referred to PHP 6, even though it never launched. Releasing a new stable version with the same number would have caused problems.

The decision to call the next version PHP 7 sent a message: this was a new and working version, not a continuation of a failed plan.