get-client-lang.php

/**
 * Return available client language choosen from $availableLanguages array
 */
function getClientLanguage($availableLanguages = null, $default='en'){
  // Keeps BC and looks for embedded function instead of pass a parameter
  $availableLanguages = $availableLanguages ?: getAvailableLanguages();

	if (isset($_SERVER['HTTP_ACCEPT_LANGUAGE'])) {
		$langs=explode(',',$_SERVER['HTTP_ACCEPT_LANGUAGE']);
		//start going through each one
		foreach ($langs as $value){
			$choice=substr($value,0,2);
			if(in_array($choice, $availableLanguages)){
				return $choice;
			}
		}
	}
	return $default;
}