将url参数添加到codeigniter中的重定向功能

I am having an issue with redirect function in codeignitor.

I have the following code

redirect('register/?id='.$post["id"]); // It works

But when I do

redirect('register/'.$post["id"]);  // Then it says page missing.

The register page is there but it's not understanding the url parameter.I am not sure if it is htaccess issue or framework issue.

htaccess file

<IfModule mod_rewrite.c>
    Options +FollowSymLinks -Indexes
    Options -MultiViews
    RewriteEngine on
    RedirectMatch 403 ^/.*/(system/cms/cache|system/codeigniter|system/cms/config|system/cms/logs|\.git|\.hg).*$
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d

    <IfModule mod_php5.c>
        RewriteRule ^(.*)$ index.php?/$1 [L]
    </IfModule>

    <IfModule !mod_php5.c>
        RewriteRule ^(.*)$ index.php?/$1 [L]
    </IfModule>

</IfModule>

Any help is highly appreciated. Thanks in advance.