root/trunk/wpmu-settings.php

<?php
if( isset( $current_site ) && isset( $current_blog ) )
    return;

// depreciated
$wpmuBaseTablePrefix = $table_prefix;

$domain = addslashes( $_SERVER['HTTP_HOST'] );
if( substr( $domain, 0, 4 ) == 'www.' )
    $domain = substr( $domain, 4 );
if( strpos( $domain, ':' ) ) {
    if( substr( $domain, -3 ) == ':80' ) {
        $domain = substr( $domain, 0, -3 );
        $_SERVER['HTTP_HOST'] = substr( $_SERVER['HTTP_HOST'], 0, -3 );
    } elseif( substr( $domain, -4 ) == ':443' ) {
        $domain = substr( $domain, 0, -4 );
        $_SERVER['HTTP_HOST'] = substr( $_SERVER['HTTP_HOST'], 0, -4 );
    } else {
        die( 'WPMU only works without the port number in the URL.' );
    }
}
$domain = preg_replace('/:.*$/', '', $domain); // Strip ports
if( substr( $domain, -1 ) == '.' )
    $domain = substr( $domain, 0, -1 );

$path = preg_replace( '|([a-z0-9-]+.php.*)|', '', $_SERVER['REQUEST_URI'] );
$path = str_replace ( '/wp-admin/', '/', $path );
$path = preg_replace( '|(/[a-z0-9-]+?/).*|', '$1', $path );

function get_current_site_name( $current_site ) {
    global $wpdb;
    $current_site->site_name = wp_cache_get( $current_site->id . ':current_site_name', "site-options" );
    if ( !$current->site->site_name ) {
        $current_site->site_name = $wpdb->get_var( $wpdb->prepare( "SELECT meta_value FROM $wpdb->sitemeta WHERE site_id = %d AND meta_key = 'site_name'", $current_site->id ) );
        if( $current_site->site_name == null )
            $current_site->site_name = ucfirst( $current_site->domain );
        wp_cache_set( $current_site->id . ':current_site_name', $current_site->site_name, 'site-options');
    }
    return $current_site;
}

function wpmu_current_site() {
    global $wpdb, $current_site, $domain, $path, $sites;
    if( defined( 'DOMAIN_CURRENT_SITE' ) && defined( 'PATH_CURRENT_SITE' ) ) {
        $current_site->id = (defined( 'SITE_ID_CURRENT_SITE' ) ? constant('SITE_ID_CURRENT_SITE') : 1);
        $current_site->domain = DOMAIN_CURRENT_SITE;
        $current_site->path   = $path = PATH_CURRENT_SITE;
        if( defined( 'BLOGID_CURRENT_SITE' ) )
            $current_site->blog_id = BLOGID_CURRENT_SITE;
        return $current_site;
    }

    $current_site = wp_cache_get( "current_site", "site-options" );
    if( $current_site )
        return $current_site;
        
    $wpdb->suppress_errors();
    $sites = $wpdb->get_results( "SELECT * FROM $wpdb->site" ); // usually only one site
    if( count( $sites ) == 1 ) {
        $current_site = $sites[0];
        $path = $current_site->path;
        $current_site->blog_id = $wpdb->get_var( "SELECT blog_id FROM {$wpdb->blogs} WHERE domain='{$current_site->domain}' AND path='{$current_site->path}'" );
        $current_site = get_current_site_name( $current_site );
        wp_cache_set( "current_site", $current_site, "site-options" );
        return $current_site;
    }
    $path = substr( $_SERVER[ 'REQUEST_URI' ], 0, 1 + strpos( $_SERVER[ 'REQUEST_URI' ], '/', 1 ) );
    if( constant( 'VHOST' ) == 'yes' ) {
        $current_site = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->site WHERE domain = %s AND path = %s", $domain, $path) );
        if( $current_site != null )
            return $current_site;
        $current_site = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->site WHERE domain = %s AND path='/'", $domain) );
        if( $current_site != null ) {
            $path = '/';
            return $current_site;
        }

        $sitedomain = substr( $domain, 1 + strpos( $domain, '.' ) );
        $current_site = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->site WHERE domain = %s AND path = %s", $sitedomain, $path) );
        if( $current_site != null )
            return $current_site;
        $current_site = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->site WHERE domain = %s AND path='/'", $sitedomain) );
        if( $current_site == null && defined( "WP_INSTALLING" ) == false ) {
            if( count( $sites ) == 1 ) {
                $current_site = $sites[0];
                die( "That blog does not exist. Please try <a href='http://{$current_site->domain}{$current_site->path}'>http://{$current_site->domain}{$current_site->path}</a>" );
            } else {
                die( "No WPMU site defined on this host. If you are the owner of this site, please check <a href='http://codex.wordpress.org/Debugging_WPMU'>Debugging WPMU</a> for further assistance." );
            }
        } else {
            $path = '/';
        }
    } else {
        $current_site = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->site WHERE domain = %s AND path = %s", $domain, $path) );
        if( $current_site != null )
            return $current_site;
        $current_site = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->site WHERE domain = %s AND path='/'", $domain) );
        if( $current_site == null && defined( "WP_INSTALLING" ) == false ) {
            if( count( $sites ) == 1 ) {
                $current_site = $sites[0];
                die( "That blog does not exist. Please try <a href='http://{$current_site->domain}{$current_site->path}'>http://{$current_site->domain}{$current_site->path}</a>" );
            } else {
                die( "No WPMU site defined on this host. If you are the owner of this site, please check <a href='http://codex.wordpress.org/Debugging_WPMU'>Debugging WPMU</a> for further assistance." );
            }
        } else {
            $path = '/';
        }
    }
    return $current_site;
}

$current_site = wpmu_current_site();
if( !isset( $current_site->blog_id ) )
    $current_site->blog_id = $wpdb->get_var( "SELECT blog_id FROM {$wpdb->blogs} WHERE domain='{$current_site->domain}' AND path='{$current_site->path}'" );

if( constant( 'VHOST' ) == 'yes' ) {
    $current_blog = wp_cache_get( 'current_blog_' . $domain, 'site-options' );
    if( !$current_blog ) {
        $current_blog = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->blogs WHERE domain = %s", $domain) );
        if( $current_blog )
            wp_cache_set( 'current_blog_' . $domain, $current_blog, 'site-options' );
    }
    if( $current_blog != null && $current_blog->site_id != $current_site->id ) {
        $current_site = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->site WHERE id = %d", $current_blog->site_id) );
    } else {
        $blogname = substr( $domain, 0, strpos( $domain, '.' ) );
    }
} else {
    $blogname = htmlspecialchars( substr( $_SERVER[ 'REQUEST_URI' ], strlen( $path ) ) );
    if( strpos( $blogname, '/' ) )
        $blogname = substr( $blogname, 0, strpos( $blogname, '/' ) );
    if( strpos( " ".$blogname, '?' ) )
        $blogname = substr( $blogname, 0, strpos( $blogname, '?' ) );
    $reserved_blognames = array( 'page', 'comments', 'blog', 'wp-admin', 'wp-includes', 'wp-content', 'files', 'feed' );
    if ( $blogname != '' && !in_array( $blogname, $reserved_blognames ) && !is_file( $blogname ) ) {
        $path = $path . $blogname . '/';
    }
    $current_blog = wp_cache_get( 'current_blog_' . $domain . $path, 'site-options' );
    if( !$current_blog ) {
        $current_blog = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->blogs WHERE domain = %s AND path = %s", $domain, $path) );
        if( $current_blog )
            wp_cache_set( 'current_blog_' . $domain . $path, $current_blog, 'site-options' );
    }
}

if( defined( "WP_INSTALLING" ) == false && constant( 'VHOST' ) == 'yes' && !is_object( $current_blog ) ) {
    if( defined( 'NOBLOGREDIRECT' ) ) {
        $destination = constant( 'NOBLOGREDIRECT' );
        if ( $destination == '%siteurl%' )
            $destination = "http://" . $current_site->domain . $current_site->path;
        header( "Location: " .  $destination);
        die();
    } else {
        if( constant( 'VHOST' ) == 'yes' ) {
            header( "Location: http://" . $current_site->domain . $current_site->path . "wp-signup.php?new=" . str_replace( '.' . $current_site->domain, '', $domain ) );
        } else {
            header( "Location: http://" . $current_site->domain . $current_site->path . "wp-signup.php?new=" . str_replace( '/', '', $_SERVER[ 'REQUEST_URI' ] ) );
        }
        die();
    }

}

if( defined( "WP_INSTALLING" ) == false ) {
    if( $current_site && $current_blog == null ) {
        if( $current_site->domain != $_SERVER[ 'HTTP_HOST' ] ) {
            header( "Location: http://" . $current_site->domain . $current_site->path );
            exit;
        }
        $current_blog = $wpdb->get_row( $wpdb->prepare("SELECT * FROM $wpdb->blogs WHERE domain = %s AND path = %s", $current_site->domain, $current_site->path) );
    }
    if( $current_blog == false || $current_site == false )
        is_installed();
}

$blog_id = $current_blog->blog_id;
$public  = $current_blog->public;

if( $current_blog->site_id == 0 || $current_blog->site_id == '' )
    $current_blog->site_id = 1;
$site_id = $current_blog->site_id;

$current_site = get_current_site_name( $current_site );

if( $blog_id == false ) {
    // no blog found, are we installing? Check if the table exists.
    if ( defined('WP_INSTALLING') ) {
    $blog_id = $wpdb->get_var( "SELECT blog_id FROM $wpdb->blogs LIMIT 0,1" );
    if( $blog_id == false ) {
        // table doesn't exist. This is the first blog
        $blog_id = 1;
    } else {
        // table exists
        // don't create record at this stage. we're obviously installing so it doesn't matter what the table vars below are like.
        // default to using the "main" blog.
        $blog_id = 1;
    }
    $current_blog->blog_id = $blog_id;
    } else {
    $check = $wpdb->get_results( "SELECT * FROM $wpdb->site" );
    if( $check == false ) {
        $msg = ': DB Tables Missing';
    } else {
        $msg = '';
    }
    die( "No Blog by that name on this system." . $msg );
    }
}

$wpdb->suppress_errors( false );

if( '0' == $current_blog->public ) {
    // This just means the blog shouldn't show up in google, etc. Only to registered members
}

function is_installed() {
    global $wpdb, $domain, $path;
    $base = stripslashes( $base );
    if( defined( "WP_INSTALLING" ) == false ) {
        $check = $wpdb->get_results( "SELECT * FROM $wpdb->site" );
        $msg = "If your blog does not display, please contact the owner of this site.<br /><br />If you are the owner of this site please check that MySQL is running properly and all tables are error free.<br /><br />";
        if( $check == false ) {
            $msg .= "<strong>Database Tables Missing.</strong><br />Database tables are missing. This means that MySQL is either not running, WPMU was not installed properly, or someone deleted {$wpdb->site}. You really <em>should</em> look at your database now.<br />";
        } else {
            $msg .= '<strong>Could Not Find Blog!</strong><br />';
            $msg .= "Searched for <em>" . $domain . $path . "</em> in " . DB_NAME . "::" . $wpdb->blogs . " table. Is that right?<br />";
        }
        $msg .= "<br />\n<h1>What do I do now?</h1>";
        $msg .= "Read the <a target='_blank' href='http://codex.wordpress.org/Debugging_WPMU'>bug report</a> page. Some of the guidelines there may help you figure out what went wrong.<br />";
        $msg .= "If you're still stuck with this message, then check that your database contains the following tables:<ul>
            <li> $wpdb->blogs </li>
            <li> $wpdb->users </li>
            <li> $wpdb->usermeta </li>
            <li> $wpdb->site </li>
            <li> $wpdb->sitemeta </li>
            <li> $wpdb->sitecategories </li>
            </ul>";
        $msg .= "If you suspect a problem please report it to the support forums but you must include the information asked for in the <a href='http://codex.wordpress.org/Debugging_WPMU'>WPMU bug reporting guidelines</a>!<br /><br />";
        if( is_file( 'release-info.txt' ) ) {
            $msg .= 'Your bug report must include the following text: "';
            $info = file( 'release-info.txt' );
            $msg .= $info[ 4 ] . '"';
        }

        die( "<h1>Fatal Error</h1> " . $msg );
    }
}

?>