if (navigator.userAgent.indexOf("Opera")!=-1) {
  language = navigator.language;
} else {
  if (navigator.appName == "Netscape") {
    language = navigator.language;
  } else {
    language = navigator.browserLanguage;
  }
}

if (language) {
  language = language.substring(0,2);
} else {
  language = "zz";
}

switch(language){
  case "en" : $lang = "en"; break;
  case "es" : $lang = "es"; break;
  case "ca" : $lang = "ca"; break;
  case "zz" : $lang = "en"; break;
  default :  $lang = "en";
}