JIT in PHP

This is the last article in a series I’ve written about understanding how PHP works. In this article, we will cover JIT in PHP.

For some background, I recommend my previous posts on this topic:

• The Magic Behind PHP
• OPcache and Preloading in PHP
• JIT Compiler in PHP

I’ve covered JIT before, so for this article, I’ll just share my slide notes.

Function JIT problems

• Generally only improves the performance of CPU-bound apps
• JIT works better with strict types (use strict_types = 1)
• Function-based JIT can’t refer to objects
• JIT is useful with real hot-spots
• Doesn’t check whether the code is frequently used or not
• Need a smarter way (Tracing JIT)

JIT-friendly code

• Strictly typed code and functions with scalar types can help JIT to infer types and make use of CPU registers.
• Use declare(strict_types=1);

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