How to execute a script in web root [b] from web root [a]

Hello,
I have two vhosts in Apache (perfect setup debian lenny).

1. www.example.com
2. foo.example.com

They both have their individual web roots.

1. Has this web root

/var/www/clients/client1/web4/web/

2. The other has

/var/www/clients/client1/web7/web/

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Ok, so now what I need to do is to execute a script that is in the root of web7 from a script that runs in the root of web4.

How may I go about this?

 

What kind of script? A shell script, a PHP script, a Perl script, etc.?

 

falko, it is a php script.

The reason is that I can't seem to get subdomains working using ISPConfig 3 so I created a new website for the forum.

So the URL to the main site is www.example.com and the forum has forum.example.com

 

Take a look at the Alias directive: http://httpd.apache.org/docs/2.2/mod/mod_alias.html#alias