sunrise.php

<?php
/**
 * In theory should support the following subdir sites as port of a subdomain network:
 * - subdomain.example.org/site1
 * - subdomain.example.org/site2
 */
function can_i_haz_subdomain_and_subdir() {
	global $wpdb, $current_blog, $current_site, $blog_id, $site_id;

	// Taken from ms-settings.php
	$domain = $_SERVER['HTTP_HOST'];
	$path = preg_replace( '|([a-z0-9-]+.php.*)|', '', $_SERVER['REQUEST_URI'] );
	$path = str_replace ( '/wp-admin/', '/', $path );
	$path = preg_replace( '|(/[a-z0-9-]+?/).*|', '$1', $path );
	$path = rtrim( $path, '/' ) . '/'; // trailingslashit

	// Currently supports one subdomain only
	if ( $domain != 'something.example.org' )
		return;

	$blog = get_blog_details( array( 'domain' => $domain, 'path' => $path ), false );

	if ( ! $blog )
		return;

	// Make WordPress think this is the right blog/site pair.
	$current_blog = $blog;
	$blog_id = $current_blog->blog_id;
	$site_id = $current_blog->site_id;

	// See ms-settings.php and mu domain mapping plugin.
	$current_site = $wpdb->get_row( $wpdb->prepare( "SELECT * from $wpdb->site WHERE id = %d LIMIT 1", $current_blog->site_id ) );
	$current_site->blog_id = $wpdb->get_var( $wpdb->prepare( "SELECT blog_id FROM $wpdb->blogs WHERE domain = %s AND path = %s LIMIT 1", $current_site->domain, $current_site->path ) );
	$current_site = get_current_site_name( $current_site );
}

can_i_haz_subdomain_and_subdir();