MODX site together with another subsite

RewriteEngine On
#make sure we have a HTTP_HOST request header
RewriteCond %{HTTP_HOST}  !^$
#only redirect requests for www.mysite.com
RewriteCond %{HTTP_HOST} ^www\.mysite\.com$ [NC]
#and if not in the modx directory
RewriteCond %{REQUEST_FILENAME} !/modx/.*$ [NC]
#and not in the theOtherSite directory
RewriteCond %{REQUEST_FILENAME} !/theOtherSite/.*$ [NC]
#from original modx rewrite
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
#only then redirect to modx index page
RewriteRule ^([^/].*) modx/index.php?q=$1 [L,QSA]


#assuming there's no modx cms on www.theOtherSite.com
RewriteCond %{HTTP_HOST}  !^$
RewriteCond %{HTTP_HOST} ^www\.theOtherSite\.com$ [NC]
#if not already in the theOtherSite directory
RewriteCond %{REQUEST_FILENAME} !/theOtherSite/.*$ [NC]
#only then redirect to theOtherSite directory
RewriteRule ^([^/].*) theOtherSite/$1

<?php
if( $_SERVER['HTTP_HOST'] == 'www.theOtherSite.com' )
    header("location: /theOtherSite/index.php");
else
    header("location: /modx/index.php");
?>