DirectoryIndex sign-in.php

<IfModule mod_rewrite.c>
    RewriteEngine on

    # HTTPS'den HTTP'ye yönlendirme
    RewriteCond %{HTTPS} on
    RewriteRule ^ http://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_FILENAME}.php -f
    RewriteRule ^(.*)$ $1.php

    RewriteRule ^([a-z]+)\/?$ $1.php [NC]
</IfModule>

ErrorDocument 404 /404.php
ErrorDocument 500 /404.php