PHP判断是不是https协议

function is_HTTPS(){  //判断是不是https
            if(!isset($_SERVER['HTTPS']))  return FALSE;  
            if($_SERVER['HTTPS'] === 1){  //Apache  
                return TRUE;  
            }elseif($_SERVER['HTTPS'] === 'on'){ //IIS  
                return TRUE;  
            }elseif($_SERVER['SERVER_PORT'] == 443){ //其他  
                return TRUE;  
            }  
                return FALSE;  
   }