bp_signup_get_subdomain_base()

	function bp_signup_get_subdomain_base() {
		global $current_site;

		// In case plugins are still using this filter.
		$subdomain_base = apply_filters( 'bp_blogs_subdomain_base', preg_replace( '|^www\.|', '', $current_site->domain ) . $current_site->path );

		/**
		 * Filters the base URL for subdomain installations of WordPress Multisite.
		 *
		 * @since BuddyPress 2.1.0
		 *
		 * @param string $subdomain_base The base URL - eg, 'example.com' for
		 *                               site_url() example.com or www.example.com.
		 */
		return apply_filters( 'bp_signup_subdomain_base', $subdomain_base );
	}