Detect browser language

Language.php

function get_client_language($availableLanguages, $default='en')
{
  if (isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
		$langs=explode(',',$_SERVER['HTTP_ACCEPT_LANGUAGE']);

		foreach ($langs as $value){
			$choice=substr($value,0,2);
			if(in_array($choice, $availableLanguages)){
				return $choice;
			}
		}
	} 

	return $default;
}