php获取header头

      $ignore = array('host','accept','content-length','content-type');

        $headers = array();

        foreach($_SERVER as $key=>$value){
            if(substr($key, 0, 5)==='HTTP_') {
                $key = substr($key, 5);
                $key = str_replace('_', ' ', $key);
                $key = str_replace(' ', '-', $key);
                $key = strtolower($key);

                if (!in_array($key, $ignore)) {
                    $headers[$key] = $value;
                }
            }
        }