Working with the JIT compiler

PHP 8 introduces the long-awaited JIT compiler. This is an important step and has important ramifications for the long-term viability of the PHP language. Although PHP already had the ability to produce and cache bytecode, before the introduction of the JIT compiler, PHP did not have the ability to directly cache machine code.

There have actually been several attempts to add JIT compiler capabilities to PHP, dating back to 2011. The performance boost seen in PHP 7 was a direct result of these early efforts. None of the earlier JIT compiler efforts were proposed as RFCs (Requests for Comments) as they didn't significantly improve performance. The core team now feels that any further performance gains can now only be achieved using JIT. As a side benefit, this opens the possibility of PHP being used as a language for non-web environments. Another benefit is that the JIT compiler opens the possibility to develop PHP extensions in languages other than...