php - How to detect root folder in URI when using apache mod_alias and mod_rewrite? -

how detect root folder in uri when using apache mod_alias , mod_rewrite?

i have website running on sub folder in of document root example /var/www/this/an/other/dir in folder have .ht_access file mod_rewrite rules redirect index.php

# nothing if file (s), link (l) or (d) exists rewritecond %{request_filename} -s [or] rewritecond %{request_filename} -l [or] rewritecond %{request_filename} -d rewriterule ^.*$ - [nc,l]  # redirect else index.php rewriterule ^.*$ index.php [e=port:%{server_port},nc,l]` 

i have set alias easy access

alias /foo /var/www/this/an/other/dir 

now when go address http://host.com/foo/bar/ how can detect /foo root folder of uri?

easiest way set env variable directly within apache:

setenv aliasroot /foo 

you can access through $_env superglobal:

$root = $_env['aliasroot']; 

i don't think there reliable way in pure php.