Using OPcache to Speed Up PHP Applications

What Is OPcache?

OPcache is a PHP extension that caches compiled PHP bytecode in shared memory. Without OPcache, PHP must parse and compile every script on every request. With OPcache, compiled scripts are reused from memory.

Enable OPcache

OPcache is included with PHP but may need to be enabled:

# Check if enabled
php -m | grep OPcache

# If not enabled, install it
sudo apt install -y php8.2-opcache

Optimal Configuration

Edit /etc/php/8.2/fpm/conf.d/10-opcache.ini:

opcache.enable=1
opcache.enable_cli=0
opcache.memory_consumption=256
opcache.interned_strings_buffer=16
opcache.max_accelerated_files=10000
opcache.revalidate_freq=0
opcache.validate_timestamps=0
opcache.fast_shutdown=1
opcache.save_comments=1

Key Settings Explained

Important: Cache Invalidation

With validate_timestamps=0, PHP never checks if files changed. After deploying new code, you must restart PHP-FPM:

sudo systemctl reload php8.2-fpm

Check OPcache Status

Create a temporary status page:

<?php
$status = opcache_get_status();
echo "Memory used: " . round($status['memory_usage']['used_memory'] / 1048576, 2) . " MB\n";
echo "Memory free: " . round($status['memory_usage']['free_memory'] / 1048576, 2) . " MB\n";
echo "Cached scripts: " . $status['opcache_statistics']['num_cached_scripts'] . "\n";
echo "Hit rate: " . round($status['opcache_statistics']['opcache_hit_rate'], 2) . "%\n";

Performance Impact

OPcache typically improves PHP performance by 2-5x for frameworks like Laravel and WordPress. It is the single most impactful PHP optimization you can make.