populate_network() WordPress Function

function populate_network( $network_id = 1, $domain = '', $email = '', $site_name = '', $path = '/', $subdomain_install = false ) {
	global $wpdb, $current_site, $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->has_errors() ) {
		return $errors;
	}

	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,
			)
		);
	}

	populate_network_meta(
		$network_id,
		array(
			'admin_email'       => $email,
			'site_name'         => $site_name,
			'subdomain_install' => $subdomain_install,
		)
	);

	$site_user = get_userdata( (int) $wpdb->get_var( $wpdb->prepare( "SELECT meta_value FROM $wpdb->sitemeta WHERE meta_key = %s AND site_id = %d", 'admin_user_id', $network_id ) ) );

	/*
	 * 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 = $wpdb->insert_id;
		update_user_meta( $site_user->ID, 'source_domain', $domain );
		update_user_meta( $site_user->ID, 'primary_blog', $current_site->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;
}