PHP OPcache Management and Optimization

What is OPcache?

OPcache is a PHP extension that stores precompiled script bytecode in shared memory, reducing parse and compile overhead on each request.

ZiziCache OPcache features

Statistics and monitoring

• Memory usage: total, used, free, wasted
• Cache efficiency: hit rate, hits, misses, cached keys
• Cached scripts: number of cached PHP files
• System details: OPcache/PHP versions, host name, server software
• Interned strings: buffer size and usage

Domain usage breakdown

• WordPress core: memory used by core files
• Theme: active theme memory consumption
• Plugins: per-plugin memory usage (best-effort based on script paths)

Note: The breakdown is derived from OPcache script paths and can be approximate in multi-site or multi-domain environments.

OPcache management

Manual flush

• Flush OPcache from ZiziCache OPcache.
• Use after deployments or when PHP files change.

Automatic flush after updates (optional)

• When enabled, ZiziCache flushes OPcache after WordPress core, plugin, or theme updates.

WP-CLI

# View OPcache statistics
wp zizi-cache opcache stats

# Flush OPcache
wp zizi-cache opcache flush

# Alternative flush commands (same effect)
wp zizi-cache opcache-flush
wp zizi-cache opcache/flush

REST API

• GET /wp-json/zizi-cache/v1/opcache/stats
• POST /wp-json/zizi-cache/v1/opcache/flush
• GET /wp-json/zizi-cache/v1/opcache/domain-usage

Limits and prerequisites

• Requires the Zend OPcache PHP extension.
• Flush uses opcache_reset() and can be blocked by opcache.restrict_api.

Redis Object Cache (optional)

ZiziCache can manage Redis object cache by installing the object-cache.php drop-in and writing Redis constants to wp-config.php when enabled in the UI.

• Connections: TCP or Unix socket.
• Authentication: Redis 6+ ACL (username + password) or password-only.
• Library: Predis is bundled with the plugin.
• Status/flush: Available via REST endpoints and the admin UI.

WP-CLI

# Flush Redis (uses wp_cache_flush under the hood)
wp zizi-cache redis-flush

# Flush object cache (backend-agnostic: Redis or Memcached)
wp zizi-cache object-cache-flush

REST API

• GET /wp-json/zizi-cache/v1/redis-status
• POST /wp-json/zizi-cache/v1/redis-flush

Memcached Object Cache (optional)

ZiziCache supports both PHP extensions (memcached and legacy memcache) and automatically selects the available backend.

• Drop-in: installs object-cache.php from a backend-specific template.
• Servers: configurable host:port list or Unix socket.
• Optional security: SASL credentials and timeouts are written to wp-config.php when configured.
• Connection testing: rate-limited and validated to avoid unsafe hosts and ports.

WP-CLI

# Flush object cache (backend-agnostic: Redis or Memcached)
wp zizi-cache object-cache-flush

REST API

• GET /wp-json/zizi-cache/v1/memcached-status
• POST /wp-json/zizi-cache/v1/memcached-test
• POST /wp-json/zizi-cache/v1/memcached-flush
• GET /wp-json/zizi-cache/v1/memcached-environment

Redis vs Memcached

Only one object cache backend can be active at a time. Enabling Redis disables Memcached and vice versa.