So we'll try to clean the things :-)
Avoid using .htaccess. All the settings in a .htaccess in a directory /foo/bar can be set in apache configuration as a Directory setting (.haccess is usefull if you provide limited access on apache conf, if you own the server don't use it).
<Directory /foo/bar>(...)</Directory>
Then you can access your sites with named based virtualhosts. Verify you have this option:
NameVirtualHost *:80
When you have it nice things can start.
This will be your virtualhost for your 1st app:
<VirtualHost *:80>
ServerName app
ServerAlias www.app.somwhere.com
ServerAlias app.somwhere.com
DocumentRoot /www/app/webroot
<Directory />
Options FollowSymLinks
AllowOverride None
</Directory>
<Directory /www/app/webroot>
Options Indexes FollowSymLinks
# this prevent.htaccess reading, remove if you want .htaccess
AllowOverride None
# allow web access
Order allow,deny
allow from all
</Directory>
</VirtualHost>
Most apache settings can be define here. Only for your 1st app. Apache will serve this configuration for all requests done for the site name 'app', or 'www.app.somwhere.com', or 'app.somwhere.com'. You can define a lot of alias(ServerAlias)., and only one name (ServerName).
Then if you go in your browser and type http://app/ your browser won't find the server, so set it in your /etc/hosts. This is what every people wanting to access your app should have in the hosts file until you get a real DNS (assuming your 1st app is app.somwhere.com and the second foo.somwhere.com and 92.128.52.226is your external IP):
127.0.0.1 app.somwhere.com app foo foo.somewhere.com
92.128.52.226 app.somwhere.com app foo foo.somewhere.com
And now let's add another virtualhost for your second app:
<VirtualHost *:80>
ServerName foo
ServerAlias www.foo.somwhere.com
ServerAlias foo.somwhere.com
DocumentRoot /www/foo/webroot
<Directory />
Options FollowSymLinks
AllowOverride None
</Directory>
<Directory /www/foo/webroot>
Options Indexes FollowSymLinks
# this prevent.htaccess reading, remove if you want .htaccess
AllowOverride None
# allow web access
Order allow,deny
allow from all
</Directory>
</VirtualHost>
And etc.
Don't forget to restart your apache. No rewrite rule. nice virtualhosts is the 1st step of a nice configuration, you will be able to define rules, directory or location specific things per name used. Even php configuration can be set per virtualhost with php_value instead of a global shared one on php.ini.
type
apache2 -S
to get the list of your virtualhosts, you'll see that the first one is the 'default' one, if apache does'nt understand the name of the requested site it will serve this default one (so you could ad a specific virtualhost on top to handle theses cases).
