Diagnosing OPcache Configuration and Cache Hits

Compare OPcache configuration and hit counters in the SAPI serving real requests.

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. CLI status is often different or disabled; the first run after reset cannot show a meaningful hit rate.

Example 1: Basic Operation

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

opcache.enable=1
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

• Compare OPcache configuration and hit counters in the SAPI serving real requests.
• Check cache statistics in the target FPM worker; CLI counters are not representative.
• Profile application response times and memory under representative traffic before tuning.