styleswitcher - page blinks

<?php
if(isset($_GET[user_style])) // if user_style has been requested by the user in the url
{
      $user_style = $_GET[user_style]; // define user_style
      setcookie("user_style",$_GET[user_style],time() + (86400 * 30), "/", "", 0); // set cookie for 30 days
}else  // else if there is no user_style variable in the url
{
   if(isset($_COOKIE['user_style'])) // see if there is a cookie
      {
      	$user_style = $_COOKIE['user_style']; // if so set user_style to cookie user_style
      }else{
      	$user_style = 0; // if not use default
      }
};

$path = '<link rel="stylesheet" href="[(base_url)]assets/templates/css/';
switch($user_style){
	case 0:
    	   $path = $path.'site1.css';
           break;
	case 1:
	   $path = $path.'site2.css';
           break;           
}
/** Complete the link and echo its html code **/
echo $path.'" type="text/css"/>';
?>

<a id="selectEstilo" href=[~[*id*]~]?user_style=0>Oscuro</a>
<a id="selectEstilo" href=[~[*id*]~]?user_style=1>Claro</a>

$_GET[user_style]