Enabling and Tuning OPcache

Enable OPcache, size shared memory and validate changes with observed cache usage.

What It Does and When to Use It

Example FPM INI directives; apply changes only in the runtime that serves requests. OPcache caches compiled opcodes, JIT may optimize CPU-intensive PHP, while APCu caches application-owned values.

Requirements, Inputs and Expected Behavior

Confirm the runtime, extension, environment variables, and permissions before running the examples in production. Production restarts and invalidation rules are part of the deployment plan.

Example 1: Basic Operation

Example FPM INI directives; apply changes only in the runtime that serves requests.

opcache.enable=1
opcache.memory_consumption=256
opcache.max_accelerated_files=20000
opcache.validate_timestamps=1
opcache.revalidate_freq=2

Example 2: Behavior and Validation

Read active OPcache configuration instead of assuming the edited INI file was loaded.

<?php
$config = opcache_get_configuration();
foreach (['opcache.enable','opcache.memory_consumption','opcache.validate_timestamps'] as $name) { echo $name, ': ',var_export($config['directives'][$name] ?? null,true),PHP_EOL; }

Practical Example: Application Use

Check cache statistics in the target FPM worker; CLI counters are not representative.

<?php
$status = opcache_get_status(false);
if (!$status) { echo 'OPcache disabled for this SAPI'; exit; }
$stats=$status['opcache_statistics'];
echo 'Cached: ', $stats['num_cached_scripts']??0, ' Hits: ', $stats['hits']??0;

Important Behavior and Edge Cases

The second example highlights: Read active OPcache configuration instead of assuming the edited INI file was loaded. The practical example adds: Check cache statistics in the target FPM worker; CLI counters are not representative.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Enable OPcache, size shared memory and validate changes with observed cache usage.
• Check cache statistics in the target FPM worker; CLI counters are not representative.
• Profile application response times and memory under representative traffic before tuning.