Smartcache

Smartcache is a WordPress plugin that sets intelligent cache lifetimes for your site. It sets Cache-Control headers for CDNs and reverse proxies to cache WordPress pages for extended periods (days+), while automatically handling cache invalidations when content is updated.

Features

• Long cache lifetimes: Pages are cached for 14 days by default (configurable)
• Automatic cache invalidation: Clears cache when posts are updated, deleted, or change status
• Smart caching rules: Automatically skips caching for logged-in users, POST/PUT/DELETE requests, and authenticated requests
• Batcache integration: Works seamlessly with Batcache for additional caching layers
• CDN cache purging: Integrates with Altis Cloud to purge CDN paths on content updates
• Admin logging: View cache invalidation history in the WordPress admin

Installation

1. Install via Composer:

   composer require humanmade/smartcache

2. Or install manually by cloning this repository into your wp-content/plugins directory.

3. The plugin will activate automatically if you're using a Composer-based setup, or you can activate it through the WordPress admin.

Configuration

Adjusting Cache TTL (Time to Live)

The default cache lifetime is 14 days. You can adjust this using the smartcache.max-age filter in your theme or plugin:

// Set cache TTL to 7 days
add_filter( 'smartcache.max-age', function() {
    return 7 * DAY_IN_SECONDS;
} );

// Set cache TTL to 1 hour
add_filter( 'smartcache.max-age', function() {
    return HOUR_IN_SECONDS;
} );

// Set cache TTL to 30 days
add_filter( 'smartcache.max-age', function() {
    return 30 * DAY_IN_SECONDS;
} );

Controlling What Gets Cached

You can control whether a response should be cached using the smartcache.should_cache filter:

// Disable caching for specific pages
add_filter( 'smartcache.should_cache', function( $should_cache ) {
    if ( is_page( 'no-cache-page' ) ) {
        return false;
    }
    return $should_cache;
} );

By default, the plugin will not cache responses for:

• Logged-in users
• POST, PUT, or DELETE requests
• Requests with HTTP Authorization headers

Customizing URLs to Invalidate

When a post is updated, the plugin invalidates its permalink by default. You can add additional URLs to invalidate using the smartcache.urls_to_invalidate_for_post filter:

// Invalidate additional URLs when a post is updated
add_filter( 'smartcache.urls_to_invalidate_for_post', function( $urls, $post_id ) {
    // Invalidate the homepage
    $urls[] = home_url( '/' );
    
    // Invalidate category archives
    $categories = get_the_category( $post_id );
    foreach ( $categories as $category ) {
        $urls[] = get_category_link( $category->term_id );
    }
    
    return $urls;
}, 10, 2 );

WP-CLI Commands

Smartcache includes WP-CLI commands for managing cache:

# View available commands
wp smartcache

Requirements

• PHP 8.0 or higher
• WordPress (tested with modern versions)

How It Works

1. Cache Headers: On each request, Smartcache sets a Cache-Control header with s-maxage for CDN/proxy caching and must-revalidate. When Batcache is available, it also sets max-age for browser caching
2. Content Updates: When a published post is updated, trashed, deleted, or changes to any other status, the plugin queues cache invalidation
3. Invalidation: URLs are purged from both Batcache (if available) and the CDN cache
4. Logging: All invalidation attempts are logged and viewable in the WordPress admin

License

GPL-2.0-or-later

Credits

Created by Joe Hoyle for Human Made