index.php not removing https CodeIgniter

index.php is not removing while i use https but it works for http. What I need to do is my site work properly such as it works on http and https both. Anybody faced same issue help me to fix this.

Ex: In http

1. http://xyz.mydomain.com/users/login //works fine
2. http://xyz.mydomain.com/index.php/users/login //works fine

IN https

1) https://xyz.mydomain.com/users/login // 404 page not found
2) https://xyz.mydomain.com/index.php/users/login // works fine

MY htaccess code

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]
</IfModule>

config.php My base url is set as

$root=(isset($_SERVER['HTTPS']) ? "https://" : "http://").$_SERVER['HTTP_HOST'];
$root.= str_replace(basename($_SERVER['SCRIPT_NAME']), '', $_SERVER['SCRIPT_NAME']);
$config['base_url'] = $root;