I just want to hide the dir name from URL.
From: example.com/dirname/somepage
To: example.com/somepage
This should be your complete .htaccess:
Options +FollowSymLinks -MultiViews
# Turn mod_rewrite on
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME}.php -f
RewriteCond %{REQUEST_URI} !/$
RewriteRule (.*) $1\.php [L]
RewriteCond %{THE_REQUEST} ^[A-Z]{3,}\s/+dirname/([^\s]+) [NC]
RewriteRule ^ %1 [R=301,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule (?!^dirname/)^(.*)$ /dirname/$1 [L,NC]