One apache server, one document root per virtual host, multiple/conditional PHP environments
		Date: 09/05/06 
		(Apache)    Keywords: php, html, web, apache
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php 
This is a very simple trick I came up with for my test environment at home.  It's used with Apache 2.* with the virtual host module loaded in httpd.conf and a virtualhost.conf file included at the end.
The trick is this:
Say you have your virtual host sites in this directory structure.
/websites/users/myDomain.com/public_html/
At 
/websites/
create two junctions/links to /websites/users/
/websites/php4 -> /websites/users/
/websites/php5 -> /websites/users/
Now use the following conf file.
ScriptAlias /php4/ "d:/wamp/php4/"
ScriptAlias /php5/ "d:/wamp/php5/"
    Options Indexes FollowSymLinks
    AllowOverride all
    Order Deny,Allow
    Deny from all
    Allow from 127.0.0.1
#Tell php where to find INI settings
    SetEnv PHPRC "d:/wamp/php4" 
#Tell Apache to process this mime with this CGI parser
    Action application/x-httpd-php "/php4/php.exe"    
 Options Indexes FollowSymLinks
 AllowOverride all
 Order Deny,Allow
 Deny from all
 Allow from 127.0.0.1
#Tell php where to find INI settings
    SetEnv PHPRC "d:/wamp/php5" 
#Tell Apache to process this mime files with this CGI parser
    Action application/x-httpd-php "/php5/php-cgi.exe"
#Tell's apache files of this type are php mime type
AddType application/x-httpd-php .php .phtml .php3
#if a broswer calls the server with http://php(4||5).myDomain.com it parses out to
#d:/website/php(4||5)/myDomain.com/public_html/
VirtualDocumentRoot "d:/website/%1/%2+/public_html/"
So now when you setup your hosts or local DNS server, you can run the same website/application in either environment by
changing out the subdomain.  And further more, there is no way to mistake what environment your in or the need to have multiple copies of websites.
Best of all, you can make other junction/links and Directory statements in Apache so you could test your site on just about every version of PHP there is.
So
http://php4.myWebsite.com/ would run the website with php4 
http://php5.myWebsite.com/ would run the website with php5
I tested this out on XP 64, but because the idea is universal, it should work on *nix environments as well.  I made a project log of setting this up along with phpDocumentor and subversion, so if anyone is interested just contact me.
Source: http://community.livejournal.com/apache/34417.html