request headers

//  $header = $request->headers;
//  kint($header);
//  "authorization"    ""
// "host"    "localhost"
// "user-agent"    "Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0"
// "accept"    "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"
// "accept-language"    "zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2"
// "accept-encoding"    "gzip, deflate"
// "cookie"    "SESScb7b6df3ee5e74077e29ed3db02cc809=Bg00-GS2GlC5WER35UyEw1LXpBecJM-GsOHOQN2i-rs; SESS69294397ac54ad21ee08e43b6a520f79=A0vbfpEvrSdLWqYqvyKbVFmCCvtPBrqkKoo21xJVun4"
// "connection"    "keep-alive"
// "upgrade-insecure-requests"    "1"
// "cache-control"