Complete reference for all WordPress Multisite API functions.

Site Retrieval Functions

get_site()

Retrieves site data given a site ID or site object.

get_site( $site = null ): WP_Site|null

Parameters:

• $site (WP_Site|int|null) – Site to retrieve. Default: current site

Returns: WP_Site object or null if not found

Example:

// Get current site
$site = get_site();

// Get specific site
$site = get_site( 5 );

// Access properties
echo $site->domain;
echo $site->path;
echo $site->blogname; // Requires full details

Source: ms-site.php

get_sites()

Retrieves a list of sites matching requested arguments.

get_sites( $args = array() ): WP_Site[]|int[]|int

Parameters:

• $args (array) – Query arguments (see WP_Site_Query)

Common Arguments:

Returns: Array of WP_Site objects, site IDs, or count

Example:

// Get all public, active sites
$sites = get_sites( array(
    'public'   => 1,
    'archived' => 0,
    'spam'     => 0,
    'deleted'  => 0,
    'number'   => 100,
) );

// Count sites
$count = get_sites( array(
    'network_id' => 1,
    'count'      => true,
) );

// Get site IDs only
$ids = get_sites( array(
    'fields' => 'ids',
) );

Source: ms-site.php

get_blog_details()

Retrieves the details for a blog from the blogs table and blog options.

get_blog_details( $fields = null, $get_all = true ): WP_Site|false

Parameters:

• $fields (int|string|array) – Blog ID, slug, or array of fields. Default: current blog
• $get_all (bool) – Retrieve all details including options. Default: true

Returns: WP_Site object or false

Example:

// By ID
$blog = get_blog_details( 5 );

// By slug
$blog = get_blog_details( 'myblog' );

// By domain/path
$blog = get_blog_details( array(
    'domain' => 'example.com',
    'path'   => '/blog/',
) );

// Access extended properties (when $get_all = true)
echo $blog->blogname;
echo $blog->siteurl;
echo $blog->home;
echo $blog->post_count;

Source: ms-blogs.php

get_site_by_path()

Retrieves the closest matching site by domain and path.

get_site_by_path( $domain, $path, $segments = null ): WP_Site|false

Parameters:

• $domain (string) – Domain to check
• $path (string) – Path to check
• $segments (int|null) – Path segments to use

Returns: WP_Site or false

Example:

$site = get_site_by_path( 'example.com', '/blog/about/' );

Source: ms-load.php

get_blog_id_from_url()

Gets a blog’s numeric ID from its URL.

get_blog_id_from_url( $domain, $path = '/' ): int

Parameters:

• $domain (string) – Website domain
• $path (string) – Path. Default: ‘/’

Returns: Blog ID or 0 if not found

Example:

$blog_id = get_blog_id_from_url( 'blog.example.com', '/' );
$blog_id = get_blog_id_from_url( 'example.com', '/myblog/' );

Source: ms-functions.php

get_id_from_blogname()

Retrieves a site’s ID given its slug.

get_id_from_blogname( $slug ): int|null

Parameters:

• $slug (string) – Site’s slug (subdomain or subdirectory name)

Returns: Site ID or null

Example:

$id = get_id_from_blogname( 'myblog' );

Source: ms-blogs.php

get_current_blog_id()

Retrieve the current site ID.

get_current_blog_id(): int

Returns: Current blog ID

Example:

$blog_id = get_current_blog_id();

Source: Core (not multisite-specific but essential)

get_blogaddress_by_id()

Gets a full site URL given a site ID.

get_blogaddress_by_id( $blog_id ): string

Parameters:

• $blog_id (int) – Site ID

Returns: Full site URL or empty string

Example:

$url = get_blogaddress_by_id( 5 );
// Returns: https://blog.example.com/

Source: ms-blogs.php

get_blogaddress_by_name()

Gets a full site URL given a site name.

get_blogaddress_by_name( $blogname ): string

Parameters:

• $blogname (string) – Name of subdomain/directory

Returns: Full URL

Example:

$url = get_blogaddress_by_name( 'myblog' );

Source: ms-blogs.php

Site Creation Functions

wp_insert_site()

Inserts a new site into the database.

wp_insert_site( array $data ): int|WP_Error

Parameters:

• $data (array) – Site data

Data Array:

Returns: Site ID or WP_Error

Example:

$site_id = wp_insert_site( array(
    'domain'     => 'example.com',
    'path'       => '/newsite/',
    'network_id' => 1,
    'user_id'    => 1,
    'title'      => 'My New Site',
    'options'    => array(
        'WPLANG' => 'en_US',
    ),
) );

Source: ms-site.php

wpmu_create_blog()

Creates a site (higher-level wrapper).

wpmu_create_blog( $domain, $path, $title, $user_id, $options = array(), $network_id = 1 ): int|WP_Error

Parameters:

• $domain (string) – Site domain
• $path (string) – Site path
• $title (string) – Site title
• $user_id (int) – Admin user ID
• $options (array) – Site options
• $network_id (int) – Network ID. Default: 1

Returns: Blog ID or WP_Error

Example:

$blog_id = wpmu_create_blog(
    'example.com',
    '/myblog/',
    'My Blog',
    1,
    array( 'public' => 1 )
);

Source: ms-functions.php

wp_initialize_site()

Runs the initialization routine for a site (creates tables, populates defaults).

wp_initialize_site( $site_id, array $args = array() ): true|WP_Error

Parameters:

• $site_id (int|WP_Site) – Site ID or object
• $args (array) – Initialization arguments

Args Array:

Returns: True on success, WP_Error on failure

Example:

wp_initialize_site( $site_id, array(
    'user_id' => 1,
    'title'   => 'New Site',
    'options' => array(
        'blogdescription' => 'A great site',
    ),
) );

Source: ms-site.php

wp_is_site_initialized()

Checks whether a site is initialized (database tables exist).

wp_is_site_initialized( $site_id ): bool

Source: ms-site.php

Site Update Functions

wp_update_site()

Updates a site in the database.

wp_update_site( $site_id, array $data ): int|WP_Error

Parameters:

• $site_id (int) – Site ID to update
• $data (array) – Site data (see wp_insert_site)

Returns: Site ID or WP_Error

Example:

wp_update_site( 5, array(
    'public' => 0,
    'spam'   => 1,
) );

Source: ms-site.php

update_blog_details()

Updates the details for a blog (wrapper for wp_update_site).

update_blog_details( $blog_id, $details = array() ): bool

Parameters:

• $blog_id (int) – Blog ID
• $details (array) – Blog details

Returns: True on success, false on failure

Source: ms-blogs.php

update_blog_status()

Updates a single blog status field.

update_blog_status( $blog_id, $pref, $value, $deprecated = null ): string|false

Parameters:

• $blog_id (int) – Blog ID
• $pref (string) – Field name
• $value (string) – New value

Allowed Fields: site_id, domain, path, registered, last_updated, public, archived, mature, spam, deleted, lang_id

Example:

update_blog_status( 5, 'public', 0 );
update_blog_status( 5, 'archived', 1 );

Source: ms-blogs.php

get_blog_status()

Gets a blog details field.

get_blog_status( $id, $pref ): bool|string|null

Source: ms-blogs.php

update_archived()

Updates the ‘archived’ status of a blog.

update_archived( $id, $archived ): string

Source: ms-blogs.php

is_archived()

Checks if a blog is archived.

is_archived( $id ): string

Source: ms-blogs.php

Site Deletion Functions

wp_delete_site()

Deletes a site from the database.

wp_delete_site( $site_id ): WP_Site|WP_Error

Parameters:

• $site_id (int) – Site ID to delete

Returns: Deleted site object or WP_Error

Example:

$deleted_site = wp_delete_site( 5 );

Source: ms-site.php

wp_uninitialize_site()

Runs the uninitialization routine (drops tables, removes uploads).

wp_uninitialize_site( $site_id ): true|WP_Error

Source: ms-site.php

Site Switching Functions

switch_to_blog()

Switches the current blog context.

switch_to_blog( $new_blog_id, $deprecated = null ): true

Parameters:

• $new_blog_id (int) – Blog ID to switch to

Returns: Always true

What Changes:

• $wpdb->prefix and table references
• Object cache context
• $blog_id global
• User capabilities (after init)

Example:

switch_to_blog( 5 );
$posts = get_posts();
$title = get_option( 'blogname' );
restore_current_blog();

Source: ms-blogs.php

restore_current_blog()

Restores the current blog after switch_to_blog().

restore_current_blog(): bool

Returns: True on success, false if no previous blog to restore

Source: ms-blogs.php

ms_is_switched()

Determines if switch_to_blog() is in effect.

ms_is_switched(): bool

Example:

if ( ms_is_switched() ) {
    // Currently in a switched context
}

Source: ms-blogs.php

Network Functions

get_network()

Retrieves network data given a network ID or object.

get_network( $network = null ): WP_Network|null

Parameters:

• $network (WP_Network|int|null) – Network to retrieve. Default: current

Returns: WP_Network or null

Example:

$network = get_network();
$network = get_network( 2 );

Source: ms-network.php

get_networks()

Retrieves a list of networks.

get_networks( $args = array() ): array|int

Parameters:

• $args (array) – Query arguments (see WP_Network_Query)

Example:

$networks = get_networks( array(
    'number' => 10,
) );

Source: ms-network.php

get_current_site()

Gets the current network.

get_current_site(): WP_Network

Source: ms-functions.php

get_current_network_id()

Gets the current network ID.

get_current_network_id(): int

Source: Core

get_network_by_path()

Retrieves the closest matching network for a domain and path.

get_network_by_path( $domain, $path, $segments = null ): WP_Network|false

Source: ms-load.php

get_main_site_id()

Gets the main site ID for a network.

get_main_site_id( $network_id = null ): int

Source: Core

Blog Options Functions

get_blog_option()

Retrieves option value for a given blog.

get_blog_option( $id, $option, $default_value = false ): mixed

Parameters:

• $id (int) – Blog ID (null = current)
• $option (string) – Option name
• $default_value (mixed) – Default if not found

Example:

$title = get_blog_option( 5, 'blogname' );

Source: ms-blogs.php

add_blog_option()

Adds a new option for a given blog.

add_blog_option( $id, $option, $value ): bool

Source: ms-blogs.php

update_blog_option()

Updates an option for a blog.

update_blog_option( $id, $option, $value, $deprecated = null ): bool

Source: ms-blogs.php

delete_blog_option()

Removes an option by name for a given blog.

delete_blog_option( $id, $option ): bool

Source: ms-blogs.php

Site Meta Functions

add_site_meta()

Adds metadata to a site.

add_site_meta( $site_id, $meta_key, $meta_value, $unique = false ): int|false

Source: ms-site.php

get_site_meta()

Retrieves metadata for a site.

get_site_meta( $site_id, $key = '', $single = false ): mixed

Source: ms-site.php

update_site_meta()

Updates metadata for a site.

update_site_meta( $site_id, $meta_key, $meta_value, $prev_value = '' ): int|bool

Source: ms-site.php

delete_site_meta()

Removes metadata from a site.

delete_site_meta( $site_id, $meta_key, $meta_value = '' ): bool

Source: ms-site.php

delete_site_meta_by_key()

Deletes all site meta matching a key.

delete_site_meta_by_key( $meta_key ): bool

Source: ms-site.php

User Functions

add_user_to_blog()

Adds a user to a blog with a specified role.

add_user_to_blog( $blog_id, $user_id, $role ): true|WP_Error

Parameters:

• $blog_id (int) – Blog ID
• $user_id (int) – User ID
• $role (string) – Role name

Example:

add_user_to_blog( 5, 10, 'editor' );

Source: ms-functions.php

remove_user_from_blog()

Removes a user from a blog.

remove_user_from_blog( $user_id, $blog_id = 0, $reassign = 0 ): true|WP_Error

Parameters:

• $user_id (int) – User ID
• $blog_id (int) – Blog ID. Default: current
• $reassign (int) – User ID to reassign posts to

Source: ms-functions.php

get_blogs_of_user()

Gets the sites a user belongs to.

get_blogs_of_user( $user_id, $all = false ): WP_Site[]

Parameters:

• $user_id (int) – User ID
• $all (bool) – Include all sites, even spam/deleted. Default: false

Returns: Array of WP_Site objects keyed by blog ID

Example:

$blogs = get_blogs_of_user( 10 );
foreach ( $blogs as $blog_id => $blog ) {
    echo $blog->blogname;
}

Source: Core user functions

get_active_blog_for_user()

Gets one of a user’s active blogs.

get_active_blog_for_user( $user_id ): WP_Site|void

Source: ms-functions.php

is_user_member_of_blog()

Determines if a user is a member of a blog.

is_user_member_of_blog( $user_id = 0, $blog_id = 0 ): bool

Source: Core user functions

is_user_spammy()

Determines whether a user is marked as spam.

is_user_spammy( $user = null ): bool

Parameters:

• $user (string|WP_User) – User login or object. Default: current

Source: ms-functions.php

Signup & Registration Functions

wpmu_validate_user_signup()

Validates user signup data.

wpmu_validate_user_signup( $user_name, $user_email ): array

Returns: Array with user_name, orig_username, user_email, errors

Source: ms-functions.php

wpmu_validate_blog_signup()

Validates blog signup data.

wpmu_validate_blog_signup( $blogname, $blog_title, $user = '' ): array

Returns: Array with domain, path, blogname, blog_title, user, errors

Source: ms-functions.php

wpmu_signup_blog()

Records site signup information for future activation.

wpmu_signup_blog( $domain, $path, $title, $user, $user_email, $meta = array() )

Source: ms-functions.php

wpmu_signup_user()

Records user signup information.

wpmu_signup_user( $user, $user_email, $meta = array() )

Source: ms-functions.php

wpmu_activate_signup()

Activates a signup.

wpmu_activate_signup( $key ): array|WP_Error

Returns: Array with blog_id/user_id, password, title, meta

Source: ms-functions.php

wpmu_create_user()

Creates a user.

wpmu_create_user( $user_name, $password, $email ): int|false

Returns: User ID or false

Source: ms-functions.php

domain_exists()

Checks whether a site name is already taken.

domain_exists( $domain, $path, $network_id = 1 ): int|null

Returns: Site ID if exists, null otherwise

Source: ms-functions.php

is_email_address_unsafe()

Checks email against banned domains.

is_email_address_unsafe( $user_email ): bool

Source: ms-functions.php

Notification Functions

wpmu_signup_blog_notification()

Sends confirmation email for new site signup.

wpmu_signup_blog_notification( $domain, $path, $title, $user_login, $user_email, $key, $meta = array() ): bool

Source: ms-functions.php

wpmu_signup_user_notification()

Sends confirmation email for new user signup.

wpmu_signup_user_notification( $user_login, $user_email, $key, $meta = array() ): bool

Source: ms-functions.php

wpmu_welcome_notification()

Notifies site admin of successful site activation.

wpmu_welcome_notification( $blog_id, $user_id, $password, $title, $meta = array() ): bool

Source: ms-functions.php

wpmu_welcome_user_notification()

Notifies user of successful account activation.

wpmu_welcome_user_notification( $user_id, $password, $meta = array() ): bool

Source: ms-functions.php

newblog_notify_siteadmin()

Notifies network admin of new site activation.

newblog_notify_siteadmin( $blog_id, $deprecated = '' ): bool

Source: ms-functions.php

newuser_notify_siteadmin()

Notifies network admin of new user activation.

newuser_notify_siteadmin( $user_id ): bool

Source: ms-functions.php

wpmu_new_site_admin_notification()

Sends email to network admin when a new site is created.

wpmu_new_site_admin_notification( $site_id, $user_id ): bool

Source: ms-functions.php

Cross-Blog Content Functions

get_blog_post()

Gets a blog post from any site on the network.

get_blog_post( $blog_id, $post_id ): WP_Post|null

Example:

$post = get_blog_post( 5, 123 );

Source: ms-functions.php

get_blog_permalink()

Gets the permalink for a post on another blog.

get_blog_permalink( $blog_id, $post_id ): string

Source: ms-functions.php

get_most_recent_post_of_user()

Gets a user’s most recent post across all their blogs.

get_most_recent_post_of_user( $user_id ): array

Returns: Array with blog_id, post_id, post_date_gmt, post_gmt_ts

Source: ms-functions.php

Statistics Functions

get_sitestats()

Gets the network’s site and user counts.

get_sitestats(): int[]

Returns: Array with blogs and users counts

Source: ms-functions.php

get_blog_count()

Gets the number of active sites on the installation.

get_blog_count( $network_id = null ): int

Source: ms-functions.php

get_user_count()

Gets the number of users on the network.

get_user_count( $network_id = null ): int

Source: Core

wp_count_sites()

Counts sites grouped by status.

wp_count_sites( $network_id = null ): int[]

Returns: Array with all, public, archived, mature, spam, deleted

Source: ms-blogs.php

get_last_updated()

Gets a list of most recently updated blogs.

get_last_updated( $deprecated = '', $start = 0, $quantity = 40 ): array

Source: ms-blogs.php

Upload & Space Functions

get_space_used()

Returns the space used by the current site in megabytes.

get_space_used(): int

Source: ms-functions.php

get_space_allowed()

Returns the upload quota for the current blog in megabytes.

get_space_allowed(): int

Source: ms-functions.php

get_upload_space_available()

Returns available upload space in bytes.

get_upload_space_available(): int

Source: ms-functions.php

is_upload_space_available()

Determines if there is any upload space left.

is_upload_space_available(): bool

Source: ms-functions.php

upload_is_file_too_big()

Checks whether an upload is too big.

upload_is_file_too_big( $upload ): string|array

Source: ms-functions.php

upload_size_limit_filter()

Filters the maximum upload file size.

upload_size_limit_filter( $size ): int

Source: ms-functions.php

check_upload_mimes()

Checks MIME types against allowed list.

check_upload_mimes( $mimes ): array

Source: ms-functions.php

Network Count Functions

wp_update_network_counts()

Updates all network-wide counts.

wp_update_network_counts( $network_id = null )

Source: ms-functions.php

wp_update_network_site_counts()

Updates the network-wide site count.

wp_update_network_site_counts( $network_id = null )

Source: ms-functions.php

wp_update_network_user_counts()

Updates the network-wide user count.

wp_update_network_user_counts( $network_id = null )

Source: ms-functions.php

wp_maybe_update_network_site_counts()

Updates site counts if enabled.

wp_maybe_update_network_site_counts( $network_id = null )

Source: ms-functions.php

wp_maybe_update_network_user_counts()

Updates user counts if enabled.

wp_maybe_update_network_user_counts( $network_id = null )

Source: ms-functions.php

wp_is_large_network()

Determines whether this is a large network.

wp_is_large_network( $using = 'sites', $network_id = null ): bool

Parameters:

• $using (string) – ‘sites’ or ‘users’
• $network_id (int|null) – Network ID

Returns: True if >10,000 sites/users

Source: ms-functions.php

Cache Functions

clean_blog_cache()

Clears the blog cache.

clean_blog_cache( $blog )

Parameters:

• $blog (WP_Site|int) – Site object or ID

Source: ms-site.php

refresh_blog_details()

Clears the blog details cache (wrapper for clean_blog_cache).

refresh_blog_details( $blog_id = 0 )

Source: ms-blogs.php

clean_site_details_cache()

Cleans the site details cache.

clean_site_details_cache( $site_id = 0 )

Source: ms-blogs.php

update_site_cache()

Updates sites in cache.

update_site_cache( $sites, $update_meta_cache = true )

Source: ms-site.php

update_sitemeta_cache()

Updates metadata cache for site IDs.

update_sitemeta_cache( $site_ids ): array|false

Source: ms-site.php

clean_network_cache()

Removes a network from the object cache.

clean_network_cache( $ids )

Source: ms-network.php

update_network_cache()

Updates the network cache.

update_network_cache( $networks )

Source: ms-network.php

wp_cache_set_sites_last_changed()

Sets the last changed time for the ‘sites’ cache group.

wp_cache_set_sites_last_changed()

Source: ms-site.php

Utility Functions

is_subdomain_install()

Whether a subdomain configuration is enabled.

is_subdomain_install(): bool

Source: ms-load.php

is_multisite()

Whether Multisite is enabled.

is_multisite(): bool

Source: Core

is_main_site()

Whether this is the main site of the network.

is_main_site( $site_id = null, $network_id = null ): bool

Source: Core

is_main_network()

Whether this is the main network.

is_main_network( $network_id = null ): bool

Source: Core

ms_site_check()

Checks status of current blog (deleted, inactive, archived, spammed).

ms_site_check(): true|string

Returns: True on success, or drop-in file path

Source: ms-load.php

get_subdirectory_reserved_names()

Retrieves reserved site names for subdirectory installations.

get_subdirectory_reserved_names(): string[]

Returns: Array including ‘wp-admin’, ‘wp-content’, ‘wp-includes’, ‘wp-json’, etc.

Source: ms-functions.php

wp_get_active_network_plugins()

Returns array of network plugin files to include.

wp_get_active_network_plugins(): string[]

Source: ms-load.php

users_can_register_signup_filter()

Determines if users can self-register.

users_can_register_signup_filter(): bool

Source: ms-functions.php

wpmu_update_blogs_date()

Updates the last_updated field for the current site.

wpmu_update_blogs_date()

Source: ms-blogs.php

update_posts_count()

Updates a blog’s post count.

update_posts_count( $deprecated = '' )

Source: ms-functions.php

wpmu_log_new_registrations()

Logs new site registration information.

wpmu_log_new_registrations( $blog_id, $user_id )

Source: ms-functions.php

redirect_this_site()

Ensures current site’s domain is in allowed redirect hosts.

redirect_this_site( $deprecated = '' ): string[]

Source: ms-functions.php

maybe_redirect_404()

Corrects 404 redirects when NOBLOGREDIRECT is defined.

maybe_redirect_404()

Source: ms-functions.php

maybe_add_existing_user_to_blog()

Adds a user via /newbloguser/{key}/ URL.

maybe_add_existing_user_to_blog()

Source: ms-functions.php

add_existing_user_to_blog()

Adds a user to the current blog.

add_existing_user_to_blog( $details = false ): true|WP_Error|void

Source: ms-functions.php

add_new_user_to_blog()

Adds a newly created user to the appropriate blog.

add_new_user_to_blog( $user_id, $password, $meta )

Source: ms-functions.php

fix_phpmailer_messageid()

Corrects mail From host to match site domain.

fix_phpmailer_messageid( $phpmailer )

Source: ms-functions.php

update_blog_public()

Updates blog’s ‘public’ setting in global blogs table.

update_blog_public( $old_value, $value )

Source: ms-functions.php

force_ssl_content()

Determines whether to force SSL on content.

force_ssl_content( $force = null ): bool

Source: ms-functions.php

filter_SSL()

Formats a URL to use https.

filter_SSL( $url ): string

Source: ms-functions.php

Deprecated Functions

wp_get_network()

Deprecated: 4.7.0 – Use get_network() instead.

get_current_site_name()

Deprecated: 3.9.0 – Use get_current_site() instead.

wpmu_current_site()

Deprecated: 3.9.0