If you want to "mask" a URL say contents in http://myurl.com/index.php would pull the content of http://myurl2.com/index.php so when you view http://myurl.com/index.php you are actually viewing http://myurl2.com but URL stays in http://myurl.com. You can do this using Apache's Mod_Rewrite via Mod_Proxy.
You should also enable dependent modules like
Then in your .htaccess in http://myurl.com/ you can do something like:
RewriteRule ^path/to/myurl/(.*)$ http://myurl2/$1 [P,L]
Remember the P flag which stands for proxy!!