I want to set a default variable for a query that comes at the end of a url

The .htaccess file redirects the url as follows:

```
http://www.server.com/folder/subfolder/index.php?page="some-page-name"

```

displayed url

```
http://www.server.com/folder/some-page-name

```

if the page name is not set, as in:

```
http://www.server.com/folder/

```

the default would be "index". I could use php function `header("location:url")` but that would display the "index" part at the end if the url... that I don't want.

htacess content

```
   Options -Indexes

    <IfModule mod_rewrite.c>
    RewriteEngine On
    #RewriteCond %{REQUEST_URI} !^(/index\.php|/img|/js|/css|/robots\.txt|/favicon\.ico)
    RewriteBase /folder/
    RewriteRule ^index\.php$ - [L]
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_URI} !^.*\.css.*$ [NC]
    RewriteRule ^(.*)$ subfolder/index.php/?page=$1 [L]
    </IfModule>

    <IfModule mod_rewrite.c> 
    ErrorDocument 404 /error.html
    ErrorDocument 403 /error.html
    </IfModule>

```