Two mod-rewrite rules

Answer 1

RewriteCond %{REQUEST_URI} !^/admin/
RewriteCond %{QUERY_STRING} (.*)
RewriteRule ^(.*/)([^/]+)/([^/]+) $1?$2=$3&%1 [L]
RewriteCond %{REQUEST_URI} !^/admin/
RewriteCond %{QUERY_STRING} (.*)
RewriteRule ^([^/]+)/ $1.php?%1 [L]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^admin/([a-z]+?)/([a-z]+?)/(.*)$ /admin/index.php?model=$1&view=$2&params=$3 [L,NS]

Answer 2

I’d use this:

RewriteEngine On

# /admin/ rule
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^admin/([a-z]+)/([a-z]+)/(.*)$ admin/index.php?model=$1&view=$2&params=$3 [L,NS]
RewriteRule ^admin/ - [L]

# other rules
RewriteRule ^(.*/)([^/]+)/([^/]+)$ $1?$2=$3 [L,QSA]
RewriteRule ^([^/]+)/ $1.php [L,QSA]

The QSA flag (query string append) replace the RewriteCond %{QUERY_STRING} (.*) directives.