Custom Flags

While built-in flags cover common cases, custom flags let you target cache clearing based on your specific content structure and business logic.

Adding Custom Flags#Copied!

Via Filter#Copied!

The millicache_flags_for_request filter runs when a page is being cached:

 1add_filter( 'millicache_flags_for_request', function( $flags ) {
 2    // Add a flag based on the page template
 3    if ( is_page_template( 'templates/landing.php' ) ) {
 4        $flags[] = 'template:landing';
 5    }
 6
 7    // Add a flag for pages with a specific Gutenberg block
 8    if ( is_singular() && has_block( 'my-plugin/hero-banner' ) ) {
 9        $flags[] = 'block:hero-banner';
10    }
11
12    return $flags;
13} );

Via PHP Function#Copied!

Add flags dynamically during template rendering:

 1// In your theme's template file
 2if ( is_product() ) {
 3    millicache_add_flag( 'woo:product' );
 4    millicache_add_flag( 'woo:product:' . get_the_ID() );
 5}
 6
 7// Based on custom logic
 8if ( get_field( 'show_pricing_table' ) ) {
 9    millicache_add_flag( 'feature:pricing' );
10}

Via Rule Action#Copied!

Use MilliRules for condition-based flag assignment:

 1use MilliCacheDepsMilliRulesRules;
 2
 3Rules::create( 'mysite:seasonal-flag' )
 4    ->on( 'template_redirect', 25 )
 5    ->when()
 6        ->has_term( 'seasonal', 'product_cat' )
 7    ->then()
 8        ->add_flag( 'promo:seasonal' )
 9    ->register();

Learn more about the powerful Rules System.

Removing Flags#Copied!

Sometimes you need to remove a built-in flag:

 1// Via PHP function
 2if ( is_front_page() && get_option( 'custom_homepage' ) ) {
 3    millicache_remove_flag( 'home' );
 4}

 1// Via rule
 2Rules::create( 'mysite:no-archive-flag' )
 3    ->on( 'template_redirect', 30 )
 4    ->when()
 5        ->is_post_type_archive( 'product' )
 6    ->then()
 7        ->remove_flag( 'archive:post' )
 8    ->register();

Clearing Cache by Flags#Copied!

WP-CLI#Copied!

 1# Clear by specific flag
 2wp millicache clear --flag="home"
 3
 4# Clear multiple flags
 5wp millicache clear --flag="post:123,home,archive:post"
 6
 7# Clear with wildcard
 8wp millicache clear --flag="post:*"
 9wp millicache clear --flag="archive:category:*"
10
11# Multisite: Include site prefix
12wp millicache clear --flag="2:post:*"
13wp millicache clear --flag="*:home"

PHP Functions#Copied!

 1// Clear by flags
 2millicache_clear_cache_by_flags( ['home', 'archive:post'] );
 3
 4// Clear with wildcard
 5millicache_clear_cache_by_flags( 'product:*' );
 6
 7// Expire instead of delete (serves stale while regenerating)
 8millicache_clear_cache_by_flags( 'home', true );
 9
10// Mixed targets (flags, post IDs, URLs)
11millicache_clear_cache( [
12    'home',                             // Flag
13    'post:123',                         // Flag
14    123,                                // Post ID
15    'https://example.com/special-page/' // URL
16] );

Wildcard Patterns#Copied!

MilliCache supports wildcards for flexible cache clearing:

The * Wildcard#Copied!

Matches any number of characters:

Pattern Matches
post:* post:1, post:123, post:999
archive:* archive:post, archive:category:5
*:home 1:home, 2:home (multisite)
feature:* All feature flags

The ? Wildcard#Copied!

Matches exactly one character:

Pattern Matches
post:? post:1 through post:9 only
?:home Sites with single-digit IDs

Flag Design Patterns#Copied!

Hierarchical Flags#Copied!

Use a consistent naming structure for granular control:

 1// E-commerce example
 2$flags[] = 'product';                    // All products
 3$flags[] = 'product:category:5';         // Products in category 5
 4$flags[] = 'product:5:sku:ABC123';       // Specific product variant
 5
 6// Clear all products
 7millicache_clear_cache_by_flags( 'product:*' );
 8
 9// Clear category only
10millicache_clear_cache_by_flags( 'product:category:5' );

Feature Flags#Copied!

Tag pages by feature for cross-cutting concerns:

 1add_filter( 'millicache_flags_for_request', function( $flags ) {
 2    // Tag pages showing dynamic pricing
 3    if ( has_dynamic_pricing() ) {
 4        $flags[] = 'feature:dynamic-pricing';
 5    }
 6
 7    // Tag pages with real-time inventory
 8    if ( shows_inventory() ) {
 9        $flags[] = 'feature:inventory';
10    }
11
12    return $flags;
13} );
14
15// When pricing engine updates, clear all affected pages
16millicache_clear_cache_by_flags( 'feature:dynamic-pricing' );

WooCommerce Integration#Copied!

 1add_filter( 'millicache_flags_for_request', function( $flags ) {
 2    if ( function_exists( 'is_product' ) && is_product() ) {
 3        $product = wc_get_product();
 4
 5        // Tag by product type
 6        $flags[] = 'woo:' . $product->get_type();
 7
 8        // Tag if on sale
 9        if ( $product->is_on_sale() ) {
10            $flags[] = 'woo:sale';
11        }
12
13        // Tag by category
14        foreach ( $product->get_category_ids() as $cat_id ) {
15            $flags[] = 'woo:cat:' . $cat_id;
16        }
17    }
18    return $flags;
19} );
20
21// Clear all sale items when sale ends
22millicache_clear_cache_by_flags( 'woo:sale' );

Time-Based Flags#Copied!

For scheduled cache clearing:

 1add_filter( 'millicache_flags_for_request', function( $flags ) {
 2    // Add a date-based flag
 3    $flags[] = 'date:' . date( 'Y-m-d' );
 4
 5    // Add a week flag for weekly content
 6    $flags[] = 'week:' . date( 'Y-W' );
 7
 8    return $flags;
 9} );
10
11// Clear yesterday's cached content via cron
12$yesterday = date( 'Y-m-d', strtotime( '-1 day' ) );
13millicache_clear_cache_by_flags( "date:{$yesterday}" );

Best Practices#Copied!

Use Descriptive Names#Copied!

 1// Good
 2$flags[] = 'product:featured';
 3$flags[] = 'archive:sale';
 4
 5// Avoid
 6$flags[] = 'x';
 7$flags[] = '123';

Limit Flag Count#Copied!

Each flag adds storage overhead. Be selective:

 1// Good: Few targeted flags
 2$flags[] = 'post:' . $post->ID;
 3$flags[] = 'archive:' . $post->post_type;
 4
 5// Avoid: Excessive flags
 6foreach ( get_all_meta( $post->ID ) as $key => $value ) {
 7    $flags[] = "meta:{$key}:{$value}";  // Could be hundreds!
 8}

Use Wildcards for Clearing#Copied!

Instead of tracking exact flags, use patterns:

 1// Good: Use wildcard
 2millicache_clear_cache_by_flags( 'product:*' );
 3
 4// Avoid: Listing every flag
 5millicache_clear_cache_by_flags( ['product:1', 'product:2', 'product:3', ...] );

Document Your Flag Taxonomy#Copied!

Plan and document your flag structure:

Your Site's Flag Structure:
├── home              - Homepage
├── post:{id}         - Individual posts
├── archive:
│   ├── post          - Post archive
│   ├── {type}        - CPT archives
│   └── {tax}:{id}    - Taxonomy archives
├── product:
│   ├── featured      - Featured products
│   └── sale          - On-sale products
├── block:
│   ├── hero          - Pages with hero block
│   └── testimonials  - Pages with testimonials
└── feature:
    ├── pricing       - Dynamic pricing pages
    └── inventory     - Real-time inventory

Next Steps#Copied!