//
// Example: echo '<a href="?page='. $previousPage . rebuildQueryString("page,submit") .'">Prev</a>';
// This would carry over any querystrings from the current URL, minus the current
// $_GET['page'] and $_GET['submit'] keys and values if they exist
//
function rebuildQueryString($curr_vars='')
{
    if(!empty($_SERVER['QUERY_STRING']))
    {
        $parts = explode("&", $_SERVER['QUERY_STRING']);
        $curr_vars = str_replace(" ", "", $curr_vars);
        $c_vars = explode(",", $curr_vars);
        $newParts = array();
        
        foreach ($parts as $val)
        {
            $val_parts = explode("=", $val);
            if(!in_array($val_parts[0], $c_vars))
            {
            	array_push($newParts, $val);
            }
        }
        
        if(count($newParts) != 0)
        {
            $qs = "&".implode("&", $newParts);
        }
        else
        {
            return false;
        }
        return $qs;
    }
    else
    {
        return false;
    }
}

//
// Example: <a href="?page='. $previousPage . rebuildQueryString("page") .'">Prev</a>
// This would carry over any querystrings from the current URL, minus the page key and value
//
function rebuildQueryString($curr_vars='')
{
    if(!empty($_SERVER['QUERY_STRING']))
    {
        $parts = explode("&", $_SERVER['QUERY_STRING']);
        $curr_vars = str_replace(" ", "", $curr_vars);
        $c_vars = explode(",", $curr_vars);
        $newParts = array();
        
        foreach ($parts as $val)
        {
            $val_parts = explode("=", $val);
            if(!in_array($val_parts[0], $c_vars))
            {
            	array_push($newParts, $val);
            }
        }
        
        if(count($newParts) != 0)
        {
            $qs = "&".implode("&", $newParts);
        }
        else
        {
            return false;
        }
        return $qs; // this is your new created query string
    }
    else
    {
        return false;
    }
}

http://www.finalwebsites.com/snippets.php?id=6

Credit: FinalWebsites.com
The only argument is a comma separated list of querystring vars that you don't want to carry over.  At minimum you should pass the name of the var that you're appending the existing querystring(s) to so it's not included twice in the URL.

Rebuild Querystring

PHP