Updated: 28 September 2026 · Applies to: CloudLinux OS
In rare cases a site shows a 503 error or a blank page with the OPcache extension enabled, because PHP crashes while OPcache optimises certain code.
Fix
Keep OPcache but switch off its optimiser by adding this to the OPcache settings (for example opcache.ini, or Select PHP Version options on CloudLinux):
opcache.optimization_level=0
Caching still works; only the optimisation step is skipped. Also update the application and PHP, as such crashes are usually fixed in newer versions.
