Pseudo "subdirectory subsite"
I think you could use an alias in your apache virtual host, something like this

Alias /site1 /path/to/your/site1
&lt;Directory /path/to/your/site1&gt;
  Options +Indexes 
  AllowOverride All 
&lt;/Directory&gt;


Like it is suggested here https://stackoverflow.com/questions/19055372/redirect-to-a-subfolder-in-apache-virtual-host-file#19055573