HHVM (HipHop Virtual Machine) vs PHP-FPM: What are the differences?

Key Differences between HHVM and PHP-FPM

HHVM (HipHop Virtual Machine) and PHP-FPM are both alternative execution engines for PHP-based applications. While they serve similar purposes, there are several key differences between the two.

1. Performance: One of the significant differences between HHVM and PHP-FPM is performance. HHVM, developed by Facebook, is known for its superior performance and efficiency. It accomplishes this by using a just-in-time (JIT) compilation technique that converts PHP code into optimized machine code, resulting in faster execution. In contrast, PHP-FPM, which stands for PHP FastCGI Process Manager, relies on the standard PHP interpreter, making it comparatively slower.

2. Compatibility: Another difference lies in compatibility. PHP-FPM is highly compatible with the vast majority of PHP applications and frameworks. It can run almost any PHP-based application without any significant issues. On the other hand, HHVM, although compatible with many PHP applications, may require modifications and adjustments to function correctly. Some PHP extensions and libraries may not be compatible with HHVM, leading to potential compatibility issues.

3. Language Features: HHVM and PHP-FPM also differ in the language features they support. PHP-FPM supports the full range of PHP language features, including the latest PHP versions and language enhancements. HHVM, however, has evolved to introduce its own set of additional language features, called Hack. Hack supports features like strict typing, asynchronous programming, and various other modern language constructs. These language enhancements can provide developers with more flexibility and productivity, but they also require learning and adopting the Hack-specific syntax.

4. Community and Support: The community and support for HHVM and PHP-FPM also differ. PHP-FPM benefits from being the default and widely-used PHP interpreter, making it more popular and having an extensive support network. Numerous online resources, forums, and communities are available for PHP-FPM, providing ample assistance to developers. While HHVM also has a community and support base, it is comparatively smaller and more niche. Finding specific help for HHVM-related issues might be more challenging.

5. Development Activity: The development activity and updates for HHVM and PHP-FPM differ significantly. PHP-FPM is actively developed as part of the PHP project and benefits from the continuous updates and improvements of the PHP language. HHVM, however, has seen a decline in development and popularity in recent years. Facebook, the primary contributor to HHVM, has shifted focus to other projects, resulting in a slower pace of development and fewer updates.

6. Operating System Support: HHVM and PHP-FPM also differ in terms of operating system support. PHP-FPM has widespread support for various operating systems, including Linux, Windows, macOS, and others. It can be easily integrated with popular web servers like Apache and Nginx. In contrast, HHVM has limited operating system support and is primarily designed and optimized for running on Linux systems. While it can be used on other platforms, the experience and performance might not be as optimal.

In summary, HHVM and PHP-FPM differ in terms of performance, compatibility, language features, community and support, development activity, and operating system support. These differences should be considered when choosing between the two for a specific project.