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) because 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 C.

It’s extremely important to pay close attention to the details given because proper use of the new JIT compiler has the potential to greatly improve the performance of our PHP applications. Before we get into implementation details, it’s first necessary to explain how PHP executes bytecode without the JIT compiler. We’ll then show how the JIT compiler works. After this, we will be in a better position to understand the various settings and how they can be fine-tuned to produce the best possible performance for our application code.

Let’s now turn our attention to how PHP ...