When I try to run remote debugging on a Drupal CMS with a url like http://mywebserver/drupal/?q=node/add/group&DBGSESSID=0@69.20.227.118:7869, the debugger doesn't start. I'm worried it may be the rewrite rules required for Drupal, or perhaps something else present in the .htaccess file. Any suggestions would be appreciated.

#
# Apache/PHP/Drupal settings:
#

# Protect files and directories from prying eyes.
<FilesMatch "(\.(engine|inc|info|install|module|profile|po|sh|.*sql|theme|tpl(\.php)?|xtmpl)|code-style\.pl|Entries.*|Repository|Root|Tag|Template)$">
Order allow,deny
</FilesMatch>

# Don't show directory listings for URLs which map to a directory.
Options -Indexes

# Follow symbolic links in this directory.
Options +FollowSymLinks

# Customized error messages.
ErrorDocument 404 /index.php

# Set the default handler.
DirectoryIndex index.php

# Override PHP settings. More in sites/default/settings.php
# but the following cannot be changed at runtime.

# PHP 4, Apache 1.
<IfModule mod_php4.c>
php_value magic_quotes_gpc 0
php_value register_globals 0
php_value session.auto_start 0
</IfModule>

# PHP 4, Apache 2.
<IfModule sapi_apache2.c>
php_value magic_quotes_gpc 0
php_value register_globals 0
php_value session.auto_start 0
</IfModule>

# PHP 5, Apache 1 and 2.
<IfModule mod_php5.c>
php_value magic_quotes_gpc 0
php_value register_globals 0
php_value session.auto_start 0
</IfModule>

# Requires mod_expires to be enabled.
<IfModule mod_expires.c>
# Enable expirations.
ExpiresActive On
# Cache all files for 2 weeks after access (A).
ExpiresDefault A1209600
# Do not cache dynamically generated pages.
ExpiresByType text/html A1
</IfModule>

# Various rewrite rules.
<IfModule mod_rewrite.c>
RewriteEngine on

# If your site can be accessed both with and without the prefix www. you
# can use one of the following settings to force user to use only one option:
#
# If you want the site to be accessed WITH the www. only, adapt and
# uncomment the following:
# RewriteCond %{HTTP_HOST} ^example\.com$ [NC]
# RewriteRule .* http://mywebserver/ [L,R=301]
#
# If you want the site to be accessed only WITHOUT the www. prefix, adapt
# and uncomment the following:
# RewriteCond %{HTTP_HOST} ^www\.example\.com$ [NC]
# RewriteRule .* http://myserver/ [L,R=301]

# Modify the RewriteBase if you are using Drupal in a subdirectory and
# the rewrite rules are not working properly.
#RewriteBase /drupal

# Rewrite old-style URLs of the form 'node.php?id=x'.
#RewriteCond %{REQUEST_FILENAME} !-f
#RewriteCond %{REQUEST_FILENAME} !-d
#RewriteCond %{QUERY_STRING} ^id=([^&]+)$
#RewriteRule node.php index.php?q=node/view/%1 [L]

# Rewrite old-style URLs of the form 'module.php?mod=x'.
#RewriteCond %{REQUEST_FILENAME} !-f
#RewriteCond %{REQUEST_FILENAME} !-d
#RewriteCond %{QUERY_STRING} ^mod=([^&]+)$
#RewriteRule module.php index.php?q=%1 [L]

# Rewrite current-style URLs of the form 'index.php?q=x'.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?q=$1 [L,QSA]
</IfModule>

# $Id: .htaccess,v 1.81 2007/01/09 09:27:10 dries Exp $

as far as I understand, your query
http://mywebserver/drupal/?q=node/add/group&DBGSESSID=0@69.20.227.118:7869

becomes

http://mywebserver/index.php?q=/drupal/?q=node/add/group&DBGSESSID=0@69.20.227.118:7869

after mod_rewrite job (see RewriteRule ^(.*)$ index.php?q=$1 [L,QSA]) and therefore DBGSESSID won't be recognized as a get parameter.

To start debugger you may want to use Debugger Toolbar.

Thanks, that worked.