OPcache, Preloading and the JIT — PHP 8: Modern PHP Development

OPcache caches compiled bytecode in shared memory so PHP doesn't re-parse files on every request — the single biggest PHP performance setting. In production set opcache.validate_timestamps=0 (reset on deploy), give it enough memory and file slots, and consider preloading (opcache.preload) for frameworks. The JIT (8.0+) compiles hot code to machine code; it helps CPU-heavy workloads (math, image processing) but rarely speeds up typical I/O-bound web apps.

; php.ini (production)
opcache.enable=1
opcache.memory_consumption=256
opcache.interned_strings_buffer=32
opcache.max_accelerated_files=50000
opcache.validate_timestamps=0      ; restart/reload FPM on deploy
opcache.jit=tracing                ; optional; measure first
opcache.jit_buffer_size=64M

Common pitfalls

validate_timestamps=0 without reloading FPM on deploy — old code keeps running.
Too few max_accelerated_files, causing cache misses on large codebases.
Expecting the JIT to fix slow database queries.

Key points

OPcache is essential in production
Reload FPM on deploy when timestamps aren't validated
JIT helps CPU-bound code, not I/O

Further reading: PHP manual: OPcache configuration

Practice questions

Why set opcache.validate_timestamps=0 in production?

Answer

PHP stops checking file modification times on every request, saving syscalls. Code is immutable between deploys, and the deploy process reloads PHP-FPM to clear the cache.

Will enabling the JIT speed up a typical Laravel app?

Answer

Usually only slightly. Most time is spent on I/O (database, network) and framework overhead; the JIT benefits CPU-intensive code.