How to detect user language in PHP, php detects user_PHP tutorial

function getPreferredLanguage() {
 $langs = array();
 if (isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
  // break up string into pieces (languages and q factors)
  preg_match_all('/([a-z]{1,8}(-[a-z]{1,8})?)\s*(;\s*q\s*=\s*(1|0\.[0-9]+))?/i',$_SERVER['HTTP_ACCEPT_LANGUAGE'], $lang_parse);
  if (count($lang_parse[1])) {
   // create a list like "en" => 0.8
   $langs = array_combine($lang_parse[1], $lang_parse[4]);
   // set default to 1 for any without q factor
   foreach ($langs as $lang => $val) {
    if ($val === '') $langs[$lang] = 1;
   }
   // sort list based on value 
   arsort($langs, SORT_NUMERIC);
  }
 }
 //extract most important (first)
 foreach ($langs as $lang => $val) { break; }
 //if complex language simplify it
 if (stristr($lang,"-")) {$tmp = explode("-",$lang); $lang = $tmp[0]; }
 return $lang;
}