How to Configure PHP 8.4 JIT Compiler for WordPress in 2026

PHP 8.4 JIT in tracing mode delivers the best performance for WordPress. Here is how to configure it correctly for production.

Check Current PHP Version

php -v
php -r "var_dump(opcache_get_status()['jit']);"

Configure OPcache and JIT

sudo nano /etc/php/8.4/fpm/php.ini

[opcache]
opcache.enable=1
opcache.memory_consumption=256
opcache.interned_strings_buffer=32
opcache.max_accelerated_files=20000
opcache.validate_timestamps=0
; JIT tracing mode — best for WordPress
opcache.jit=tracing
opcache.jit_buffer_size=128M

Restart PHP-FPM

sudo systemctl restart php8.4-fpm

Verify JIT is Active

php8.4 -r "print_r(opcache_get_status()['jit']);"

Look for enabled: true and kind: 5 (tracing mode).

Benchmark Before and After

ab -n 500 -c 10 https://yourdomain.com/

WordPress-Specific Settings

define('WP_MEMORY_LIMIT', '512M');
define('WP_MAX_MEMORY_LIMIT', '512M');

Conclusion

PHP 8.4 JIT tracing delivers 20-30% better throughput for WordPress. Our team handles PHP upgrades and performance tuning with zero downtime.