private function header2String($header)
    {
        $str = '';
        if (is_array($header)) foreach ($header as $k=>$v) {
            if (is_numeric($k)) continue;
            $str .= $k . ': ' . $v . "\r\n";
        } else {
            $str = $header;
        }
        return $str;
    }
private function header2String($header)
    {
        $str = '';
        if (is_array($header)) foreach ($header as $k=>$v) {
            if (is_numeric($k)) continue;
            $str .= $k . ': ' . $v . "\r\n";
        } else {
            $str = $header;
        }
        return $str;
    }
private function header2String ( $ header ) { $ str = '' ; if ( is_array ( $ header ) ) foreach ( $ header as $ k => $ v ) { if ( is_numeric ( $ k ) ) continue ; $ str .= $ k . ': ' . $ v . "\r\n" ; } else { $ str = $ header ; } return $ str ; }
parse header to string
@param  mixed  $headers
@return string
parse header to string