Apache multiple DocumentRoot
Use Alias:
Alias /ABC/ /var/www/ABC/Alias /PQR/ /var/www/PQR/Leave the document root pointing to /var/www/Others/index.php. It could do the trick. :)
You can do this with mod_alias, which is part of the apache distribution.
http://httpd.apache.org/docs/current/mod/mod_alias.html
for serving everything else with the single file you would use mod_rewrite. This has many features and depending on your needs you might need to tweak that.. but something like this should work:
RewriteEngine onRewriteRule ^(.*)$ /index.php?path=$1 [L]you would put that in a .htaccess file in the document root.