WP Rocket: cache invalidation from third-party code

For developers shipping a plugin or theme that mutates content WP Rocket has cached — saving a custom CPT, completing a WooCommerce order, importing data, processing a webhook, scheduling a bulk update. WP Rocket caches HTML to disk (NOT to the WP object cache); raw cache invalidation requires going through the plugin's public API, otherwise stale HTML stays served until the cache TTL or the next save.

WP Rocket is a paid plugin, not on Packagist, not in the WordPress.org plugin directory. Many sites have it; many don't. Every code path that touches rocket_clean_* MUST be feature-detected first — otherwise your code fatals on installs without WP Rocket.

Misconception this skill corrects

"I'll call wp_cache_flush() after my plugin saves data — that clears WP Rocket too."

It doesn't. wp_cache_flush() clears the WordPress object cache (transients, options, post meta caches in Redis / Memcached / WP_Cache_Object). WP Rocket is a page cache that writes static HTML files to disk under wp-content/cache/wp-rocket/.... The two are completely independent layers — you can flush the object cache 1000 times and the WP Rocket cached HTML stays untouched.

The right entry point: rocket_clean_post( $post_id ) if a specific post changed, or one of the more granular rocket_clean_* functions for other scenarios. Verified at wp-content/plugins/wp-rocket/inc/common/purge.php:167 and inc/functions/files.php.

Other AI-prone misconceptions:

• "I'll just unlink() the WP Rocket cache files for this URL." Wrong direction — WP Rocket's filename layout is non-trivial: desktop / mobile / tablet variants, language variants (/cache/wp-rocket/example.com-en/...), query-string variants, gzipped variants, webp variants. Manual deletion misses some, leaves stale files, AND skips the before_/after_ action hooks that other plugins (CDN purgers, Varnish, Cloudflare addons) listen for.
• "function_exists('rocket_clean_post') is paranoid; everyone has WP Rocket." No, WP Rocket is paid. ~30% of WP installs use SOME caching plugin; even of those, WP Rocket is one of many. Always feature-detect.
• "is_plugin_active('wp-rocket/wp-rocket.php')" is the right check." Half-true. is_plugin_active() requires wp-admin/includes/plugin.php to be loaded — it's NOT available during early hooks like plugins_loaded. defined('WP_ROCKET_VERSION') and function_exists('rocket_clean_post') work everywhere.