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PHP-FPM — glossary

TL;DR

FastCGI Process Manager — PHP workers that serve requests behind nginx or Apache.

Key facts

Term
PHP-FPM

TL;DR

PHP-FPM (FastCGI Process Manager) runs the worker pool that executes PHP behind nginx or Apache. When the pool is exhausted, users see slow pages or 502 Bad Gateway.

Key settings

  • pm.max_children — hard cap on concurrent workers (primary capacity lever)
  • pm strategy — dynamic, ondemand, or static for different traffic shapes
  • request_slowlog_timeout — surfaces requests wedging workers

Sizing

Oversizing workers causes OOM; undersizing causes queueing. Use the PHP-FPM calculator before changing production pools.

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