WordPress Multisite Functions Reference

Last updated: February 12, 2026

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:

Argument Type Description
network_id int Network ID
domain string Site domain
path string Site path
public int Public status (0/1)
archived int Archived status
mature int Mature status
spam int Spam status
deleted int Deleted status
number int Number to return
offset int Offset
orderby string Order field
order string ASC/DESC
fields string ‘ids’ for IDs only
count bool Return count only

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:

Key Type Description
domain string Site domain
path string Site path. Default: ‘/’
network_id int Network ID. Default: current
registered string Registration date
last_updated string Last updated date
public int Public status. Default: 1
archived int Archive status. Default: 0
mature int Mature status. Default: 0
spam int Spam status. Default: 0
deleted int Deleted status. Default: 0
lang_id int Language ID. Default: 0
user_id int Admin user ID
title string Site title
options array Initial options
meta array Site metadata

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:

Key Type Description
user_id int Administrator user ID
title string Site title
options array Initial option key=>value pairs
meta array Site metadata key=>value pairs

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

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