How to make an internal redirect using a file .htaccess?

Question

I have the urls

https://example.net/app/ref/user/u123456

https://example.net/app/ref/user/u123456/

Need redirect both url to https://example.net/app/ref/user/index.php?referral=u123456

How to do it with a file .htaccess? Unfortunately, I couldn't do it, so I'm asking for your help.

UPD: Now me .htaccess is in the same directory as index.php:

<IfModule mod_rewrite.c>
  RewriteEngine on
</IfModule>
AddType application/x-httpd-php .html
<Files 403.shtml>
order allow,deny
allow from all
</Files>

Answer 1

With your shown samples please try following htaccess rules file. Please make sure you keep your .htaccess rules file in your root folder; alongside with your app folder.

Make sure to clear your browser cache before testing your URLs.

RewriteEngine ON
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^([^/]*/[^/]*/[^/]*)/([^/]*)/?$ $1/index.php?referral=$2 [QSA,L]