Check Version IE

preg_match('/MSIE (.*?);/', $_SERVER['HTTP_USER_AGENT'], $matches);

if (count($matches)>1){
  //Then we're using IE
  $version = $matches[1];

  switch(true){
    case ($version<=8):
      //IE 8 or under!
      break;

    case ($version==9):
      //IE9!
      break;

    default:
      //You get the idea
  }
}