populate_network( int $network_id = 1, string $domain = '', string $email = '', string $site_name = '', string $path = '/', bool $subdomain_install = false )

function populate_network( $network_id = 1, $domain = '', $email = '', $site_name = '', $path = '/', $subdomain_install = false ) {
	global $wpdb, $current_site, $wp_db_version, $wp_rewrite;

	$errors = new WP_Error();
	if ( '' == $domain )
		$errors->add( 'empty_domain', __( 'You must provide a domain name.' ) );
	if ( '' == $site_name )
		$errors->add( 'empty_sitename', __( 'You must provide a name for your network of sites.' ) );

	// Check for network collision.
	$network_exists = false;
	if ( is_multisite() ) {
		if ( get_network( (int) $network_id ) ) {
			$errors->add( 'siteid_exists', __( 'The network already exists.' ) );
		}
	} else {
		if ( $network_id == $wpdb->get_var( $wpdb->prepare( "SELECT id FROM $wpdb->site WHERE id = %d", $network_id ) ) ) {
			$errors->add( 'siteid_exists', __( 'The network already exists.' ) );
		}
	}

	if ( ! is_email( $email ) )
		$errors->add( 'invalid_email', __( 'You must provide a valid email address.' ) );

	if ( $errors->get_error_code() )
		return $errors;

	// If a user with the provided email does not exist, default to the current user as the new network admin.
	$site_user = get_user_by( 'email', $email );
	if ( false === $site_user ) {
		$site_user = wp_get_current_user();
	}

	// Set up site tables.
	$template = get_option( 'template' );
	$stylesheet = get_option( 'stylesheet' );
	$allowed_themes = array( $stylesheet => true );

	if ( $template != $stylesheet ) {
		$allowed_themes[ $template ] = true;
	}

	if ( WP_DEFAULT_THEME != $stylesheet && WP_DEFAULT_THEME != $template ) {
		$allowed_themes[ WP_DEFAULT_THEME ] = true;
	}

	// If WP_DEFAULT_THEME doesn't exist, also whitelist the latest core default theme.
	if ( ! wp_get_theme( WP_DEFAULT_THEME )->exists() ) {
		if ( $core_default = WP_Theme::get_core_default_theme() ) {
			$allowed_themes[ $core_default->get_stylesheet() ] = true;
		}
	}

	if ( 1 == $network_id ) {
		$wpdb->insert( $wpdb->site, array( 'domain' => $domain, 'path' => $path ) );
		$network_id = $wpdb->insert_id;
	} else {
		$wpdb->insert( $wpdb->site, array( 'domain' => $domain, 'path' => $path, 'id' => $network_id ) );
	}

	wp_cache_delete( 'networks_have_paths', 'site-options' );

	if ( !is_multisite() ) {
		$site_admins = array( $site_user->user_login );
		$users = get_users( array(
			'fields' => array( 'user_login' ),
			'role'   => 'administrator',
		) );
		if ( $users ) {
			foreach ( $users as $user ) {
				$site_admins[] = $user->user_login;
			}

			$site_admins = array_unique( $site_admins );
		}
	} else {
		$site_admins = get_site_option( 'site_admins' );
	}

	/* translators: Do not translate USERNAME, SITE_NAME, BLOG_URL, PASSWORD: those are placeholders. */
	$welcome_email = __( 'Hello USERNAME,

Your new SITE_NAME site has been successfully set up at:
BLOG_URL

You can log in to the administrator account with the following information:

Username: USERNAME
Password: PASSWORD
Log in here: BLOG_URLwp-login.php

We hope you enjoy your new site. Thanks!

--The Team @ SITE_NAME' );

	$misc_exts = array(
		// Images.
		'jpg', 'jpeg', 'png', 'gif',
		// Video.
		'mov', 'avi', 'mpg', '3gp', '3g2',
		// "audio".
		'midi', 'mid',
		// Miscellaneous.
		'pdf', 'doc', 'ppt', 'odt', 'pptx', 'docx', 'pps', 'ppsx', 'xls', 'xlsx', 'key',
	);
	$audio_exts = wp_get_audio_extensions();
	$video_exts = wp_get_video_extensions();
	$upload_filetypes = array_unique( array_merge( $misc_exts, $audio_exts, $video_exts ) );

	$sitemeta = array(
		'site_name' => $site_name,
		'admin_email' => $email,
		'admin_user_id' => $site_user->ID,
		'registration' => 'none',
		'upload_filetypes' => implode( ' ', $upload_filetypes ),
		'blog_upload_space' => 100,
		'fileupload_maxk' => 1500,
		'site_admins' => $site_admins,
		'allowedthemes' => $allowed_themes,
		'illegal_names' => array( 'www', 'web', 'root', 'admin', 'main', 'invite', 'administrator', 'files' ),
		'wpmu_upgrade_site' => $wp_db_version,
		'welcome_email' => $welcome_email,
		/* translators: %s: site link */
		'first_post' => __( 'Welcome to %s. This is your first post. Edit or delete it, then start blogging!' ),
		// @todo - network admins should have a method of editing the network siteurl (used for cookie hash)
		'siteurl' => get_option( 'siteurl' ) . '/',
		'add_new_users' => '0',
		'upload_space_check_disabled' => is_multisite() ? get_site_option( 'upload_space_check_disabled' ) : '1',
		'subdomain_install' => intval( $subdomain_install ),
		'global_terms_enabled' => global_terms_enabled() ? '1' : '0',
		'ms_files_rewriting' => is_multisite() ? get_site_option( 'ms_files_rewriting' ) : '0',
		'initial_db_version' => get_option( 'initial_db_version' ),
		'active_sitewide_plugins' => array(),
		'WPLANG' => get_locale(),
	);
	if ( ! $subdomain_install )
		$sitemeta['illegal_names'][] = 'blog';

	/**
	 * Filters meta for a network on creation.
	 *
	 * @since WP-3.7.0
	 *
	 * @param array $sitemeta   Associative array of network meta keys and values to be inserted.
	 * @param int   $network_id ID of network to populate.
	 */
	$sitemeta = apply_filters( 'populate_network_meta', $sitemeta, $network_id );

	$insert = '';
	foreach ( $sitemeta as $meta_key => $meta_value ) {
		if ( is_array( $meta_value ) )
			$meta_value = serialize( $meta_value );
		if ( !empty( $insert ) )
			$insert .= ', ';
		$insert .= $wpdb->prepare( "( %d, %s, %s)", $network_id, $meta_key, $meta_value );
	}
	$wpdb->query( "INSERT INTO $wpdb->sitemeta ( site_id, meta_key, meta_value ) VALUES " . $insert );

	/*
	 * When upgrading from single to multisite, assume the current site will
	 * become the main site of the network. When using populate_network()
	 * to create another network in an existing multisite environment, skip
	 * these steps since the main site of the new network has not yet been
	 * created.
	 */
	if ( ! is_multisite() ) {
		$current_site = new stdClass;
		$current_site->domain = $domain;
		$current_site->path = $path;
		$current_site->site_name = ucfirst( $domain );
		$wpdb->insert( $wpdb->blogs, array( 'site_id' => $network_id, 'blog_id' => 1, 'domain' => $domain, 'path' => $path, 'registered' => current_time( 'mysql' ) ) );
		$current_site->blog_id = $blog_id = $wpdb->insert_id;
		update_user_meta( $site_user->ID, 'source_domain', $domain );
		update_user_meta( $site_user->ID, 'primary_blog', $blog_id );

		if ( $subdomain_install )
			$wp_rewrite->set_permalink_structure( '/%year%/%monthnum%/%day%/%postname%/' );
		else
			$wp_rewrite->set_permalink_structure( '/blog/%year%/%monthnum%/%day%/%postname%/' );

		flush_rewrite_rules();

		if ( ! $subdomain_install )
			return true;

		$vhost_ok = false;
		$errstr = '';
		$hostname = substr( md5( time() ), 0, 6 ) . '.' . $domain; // Very random hostname!
		$page = wp_remote_get( 'http://' . $hostname, array( 'timeout' => 5, 'httpversion' => '1.1' ) );
		if ( is_wp_error( $page ) )
			$errstr = $page->get_error_message();
		elseif ( 200 == wp_remote_retrieve_response_code( $page ) )
				$vhost_ok = true;

		if ( ! $vhost_ok ) {
			$msg = '<p><strong>' . __( 'Warning! Wildcard DNS may not be configured correctly!' ) . '</strong></p>';

			$msg .= '<p>' . sprintf(
				/* translators: %s: host name */
				__( 'The installer attempted to contact a random hostname (%s) on your domain.' ),
				'<code>' . $hostname . '</code>'
			);
			if ( ! empty ( $errstr ) ) {
				/* translators: %s: error message */
				$msg .= ' ' . sprintf( __( 'This resulted in an error message: %s' ), '<code>' . $errstr . '</code>' );
			}
			$msg .= '</p>';

			$msg .= '<p>' . sprintf(
				/* translators: %s: asterisk symbol (*) */
				__( 'To use a subdomain configuration, you must have a wildcard entry in your DNS. This usually means adding a %s hostname record pointing at your web server in your DNS configuration tool.' ),
				'<code>*</code>'
			) . '</p>';

			$msg .= '<p>' . __( 'You can still use your site but any subdomain you create may not be accessible. If you know your DNS is correct, ignore this message.' ) . '</p>';

			return new WP_Error( 'no_wildcard_dns', $msg );
		}
	}

	return true;
}