htaccess similar cases like Facebook or Twitter issue - regex

Question

I have this piece of line in my htaccess that causes errors. I couldn't find a similar answer to my inadequate wording.
I am attempting to get "username/followers, username/following, etc" and also "settings/account, settings/password, etc". I stopped using sub folders for non-scripts and images, so everything is on the same level.
Now I know they have similar casing, but I am curious how Facebook, Twitter, etc manage to do this.
Do they condense to one large page to make it work? I know they prevent people from using settings and other root level names from being used, and I haven't quite gotten to that point myself.
RewriteRule ^([^/]+)$ profile_home.php?userdomain=$1 [L]
RewriteRule ^([^/]+)/([^/]+)$ profile_home.php?userdomain=$1&selection=$2 [L]
RewriteRule ^settings/$ profile_settings.php [L]
RewriteRule ^settings/([^/]+)$ profile_settings.php?selection=$1 [L]
RewriteRule ^settings/([^/]+)/([^/]+)$ profile_settings.php?selection=$1&upload=$2 [L]
If I remove
RewriteRule ^([^/]+)/([^/]+)$ profile_home.php?userdomain=$1&selection=$2 [L]
Then everything works fine. How do I make this work with two pages?
I could do
RewriteRule ^settings/([^/]+)/$ profile_settings.php?selection=$1 [L]
But it doesn't look as nice. If not right place to ask, please let me know.

Answer 1

Your second rule matches both directory structures. You can use a negative lookahead so requests starting with the setting are not matched by that rule.
^(?!settings)([^/]+)/([^/]+)$
You can read more about lookaheads here:
http://www.rexegg.com/regex-lookarounds.html
http://www.regular-expressions.info/lookaround.html

Answer 2

Here is my solution
RewriteEngine On
# make sure to add your document root dir
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([\w-.]+)/?$ index.php?id=$1 [L,QSA]
RewriteCond %{DOCUMENT_ROOT}/htdocs/user/$2 -f
RewriteRule ^([\w-]+)/(.+)/?$ $2?id=$1&goto=$2 [L,QSA]
RewriteCond %{DOCUMENT_ROOT}/htdocs/user/$2/index.php -f
RewriteRule ^([\w-.]+)/([a-z0-9]+)/?$ $2/index.php?id=$1&goto=$2 [NC,L,QSA]
RewriteRule ^([\w-.]+)/([a-z0-9]+)/?$ index.php?id=$1&goto=$2 [NC,L,QSA]
so inside your server root dir htdocs/user/ you must have a folder like /user/ and a file index.php this htacess will replace the file site/user/index.php to site/user/username in the same user dir you need to have the following.php file so site/user/username/following.php in the same folder, I think you understand my answer.