WordPress Theme License Checker

/*********************************************************************************************
**********************************************************************************************
** WordPress Theme License Checker                              **
** Author: The Sufi                                     **
** Author URI: http://www.thedct.com                                **
** Version: 1.0                                         **
**********************************************************************************************
*********************************************************************************************/
function check_point($key, $url){
    $file = "http://www.yourserver.com/xmldirectory/05a0e40e81edc455d757dd8b40127581.xml";
    $contents = file_get_contents($file);
    if (!$contents){//file not found
        wp_die('Error! Please contact theme support!');
        exit;
    }
    $xml = new SimpleXMLElement($contents);
    if ( $key == $xml->key && $url == $xml->domain ){
        return true;
    }
    else return false;
}
$key = "ejhg789Xdfg";//you should retrieve this using a text box and save to wp_options table
$domain = $_SERVER['HTTP_HOST'];//current domain
$status = check_point($key, $domain);
if (!$status){
    wp_die('invalid theme license');
}
else{
//here goes your original theme functions.php codes
}