How to Enable and Configure PHP OPcache in DirectAdmin for Faster Website Loading

PHP OPcache is one of the highest-impact, lowest-effort performance improvements you can make on a DirectAdmin server. By caching compiled PHP bytecode in shared memory, OPcache eliminates the need to parse and compile PHP scripts on every request — reducing CPU usage by 30–50% on busy servers and cutting page load times dramatically. This guide walks you through installing OPcache via DirectAdmin's CustomBuild, tuning it correctly for production workloads, and configuring it for servers running multiple PHP versions.

What PHP OPcache Does and Why It Matters

Every time a PHP script runs without OPcache, the PHP engine must:

• Read the source file from disk
• Tokenise and parse the PHP code
• Compile it to opcodes (bytecode)
• Execute those opcodes

With OPcache enabled, steps 1–3 happen only once per file (or until the file changes). The compiled opcodes are stored in shared memory and reused on subsequent requests. For a typical WordPress site with 400–800 PHP files loaded per request, this removes thousands of disk reads and compile operations per second.

The result: lower CPU, faster TTFB (Time to First Byte), and the ability to handle significantly more concurrent visitors on the same hardware.

Step 1: Check If OPcache Is Already Installed

Before installing, check whether OPcache is already present on your DirectAdmin server:

php -m | grep -i opcache

If the output shows Zend OPcache, OPcache is installed (though it may be disabled or misconfigured). Check its status:

php -i | grep -i opcache.enable

If nothing is returned or you see opcache.enable=0, proceed with installation.

Step 2: Install OPcache via DirectAdmin CustomBuild

DirectAdmin uses CustomBuild 2.0 to manage PHP extensions including OPcache. All installation is done as root via SSH.

cd /usr/local/directadmin/custombuild

./build set opcache yes

./build opcache

php -m | grep -i opcache

Step 3: Configure OPcache for Production Performance

The default OPcache settings that ship with PHP are conservative and not tuned for a busy web server. You need to edit the php.ini file for each PHP version.

Find all OPcache-enabled php.ini files:

find /usr/local/php* -name php.ini 2>/dev/null
# Also check:
find /etc/php* -name php.ini 2>/dev/null

For each php.ini file, find the [opcache] section (or add it at the bottom) and apply these settings:

[opcache]
opcache.enable=1
opcache.enable_cli=0
opcache.memory_consumption=256
opcache.interned_strings_buffer=32
opcache.max_accelerated_files=20000
opcache.revalidate_freq=60
opcache.validate_timestamps=1
opcache.save_comments=1
opcache.fast_shutdown=1
opcache.enable_file_override=0

What Each Setting Means

• opcache.enable=1 — enables OPcache for web requests (always set this to 1)
• opcache.enable_cli=0 — disables OPcache for CLI PHP (leave off unless you run long-running CLI scripts that benefit from caching)
• opcache.memory_consumption=256 — RAM (in MB) allocated to the OPcache shared memory segment. See sizing guide below
• opcache.interned_strings_buffer=32 — separate RAM pool for interned strings (class/function names). 32 MB is sufficient for most WordPress/Laravel setups
• opcache.max_accelerated_files=20000 — maximum number of PHP files OPcache can store. Must be higher than the total number of PHP files on the server
• opcache.revalidate_freq=60 — how often (in seconds) OPcache checks if a file has changed on disk. Set to 0 only in development
• opcache.validate_timestamps=1 — OPcache checks file modification time before using cached version. Keep at 1 unless you have a deployment process that flushes OPcache on deploy
• opcache.save_comments=1 — required by Doctrine, Laravel, and many frameworks that use PHP docblock annotations

Step 4: Size OPcache Memory Correctly for Your Server

The most common OPcache mistake is setting memory_consumption too low. When the cache fills up, OPcache starts evicting entries and performance degrades to near-uncached levels.

To size OPcache correctly, first count the PHP files on your server:

find /home -name "*.php" | wc -l

Then estimate the memory needed. As a rule of thumb, each PHP file consumes approximately 10–15 KB of OPcache memory after compilation. Multiply the file count by 15 KB to get a conservative estimate:

# Example: 8,000 PHP files × 15 KB = 120 MB → set memory_consumption=192

For shared hosting servers with many accounts, set memory_consumption to at least 256 MB. For large servers with 50+ WordPress installations, 512 MB is appropriate.

Check OPcache memory usage after 30 minutes of production traffic:

php -r "print_r(opcache_get_status());" | grep -E 'used_memory|free_memory|wasted'

If used_memory is within 10% of total allocated memory, increase memory_consumption. If wasted_percentage exceeds 5%, consider increasing max_wasted_percentage or restarting PHP-FPM more frequently to compact the cache.

Step 5: Configure OPcache for Multiple PHP Versions

DirectAdmin servers often run PHP 7.4, 8.1, 8.2, and 8.3 simultaneously for different user accounts. You must configure OPcache separately in each version's php.ini.

Find all PHP version ini files:

ls /usr/local/php*/lib/php.ini

Apply the same OPcache settings to each file. You can automate this with a loop:

for ini in /usr/local/php*/lib/php.ini; do
  echo "Configuring OPcache in: $ini"
  # Enable OPcache
  sed -i 's/^;opcache.enable=.*/opcache.enable=1/' "$ini"
  sed -i 's/^opcache.enable=.*/opcache.enable=1/' "$ini"
  # Set memory
  sed -i 's/^;opcache.memory_consumption=.*/opcache.memory_consumption=256/' "$ini"
  sed -i 's/^opcache.memory_consumption=.*/opcache.memory_consumption=256/' "$ini"
  # Set max files
  sed -i 's/^;opcache.max_accelerated_files=.*/opcache.max_accelerated_files=20000/' "$ini"
  sed -i 's/^opcache.max_accelerated_files=.*/opcache.max_accelerated_files=20000/' "$ini"
done

After editing any php.ini file, restart PHP-FPM for each version:

systemctl restart php-fpm74
systemctl restart php-fpm81
systemctl restart php-fpm82
systemctl restart php-fpm83

Or restart all at once:

systemctl restart 'php-fpm*'

Step 6: Verify OPcache Is Working

Create a phpinfo test file in a domain's web root:

echo " /home/USER/domains/DOMAIN/public_html/phpinfo.php

Visit https://yourdomain.com/phpinfo.php in a browser and search for "opcache". You should see a section headed Zend OPcache with Opcode Caching: Enabled.

Delete the phpinfo file immediately after testing:

rm /home/USER/domains/DOMAIN/public_html/phpinfo.php

For a more detailed status check, create a temporary monitoring script:

cat > /tmp/opcache_check.php << 'PHP'

php_flag opcache.enable 0

php_admin_value[opcache.enable] = 0