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似乎最普遍接受的将用户从http://example.com重定向到http://www.example.com的方法是通过 301 永久重定向，但我遇到了一个似乎正在使用重定向的网站（Facebook）其他一些方法。我使用PHP内置的get_headers() 函数，当我希望看到两个不同的 HTTP 代码（类似于 200 OK 和 301 永久重定向）。那么，如果 facebook.com 重定向到 www.facebook.com，为什么我会看到相同的 HTTP 响应代码？他们还可以使用哪些其他方法（不包括元刷新等明显的方法）来重定向？

以下是测试 get_headers() 的数据数组，带和不带 WWW 前缀： 

Array
(
[0] => HTTP/1.0 302 Found
[1] => Location: https://facebook.com/
[2] => Content-Type: text/html; charset=utf-8
[3] => X-FB-Debug: wwltbGRu1BTbywd3gta2SdLc+wpyGdq51OOfn2wGKPs=
[4] => Date: Tue, 30 Apr 2013 06:46:59 GMT
[5] => Connection: close
[6] => Content-Length: 0
[7] => HTTP/1.0 301 Moved Permanently
[8] => Location: https://www.facebook.com/
[9] => Content-Type: text/html; charset=utf-8
[10] => X-FB-Debug: WxvPFmdvhZu01Ksi4H9ttx0nffFCraY9TQtxscHgRlU=
[11] => Date: Tue, 30 Apr 2013 06:47:00 GMT
[12] => Connection: close
[13] => Content-Length: 0
[14] => HTTP/1.0 302 Found
[15] => Location: http://www.facebook.com/unsupportedbrowser
[16] => P3P: CP="Facebook does not have a P3P policy. Learn why here: http://fb.me/p3p"
[17] => X-Content-Type-Options: nosniff
[18] => Set-Cookie: datr=5Gh_Ue6q0jyzse8jKRbcPg2N; expires=Thu, 30-Apr-2015 06:47:00 GMT; path=/; domain=.facebook.com; httponly
[19] => Content-Type: text/html; charset=utf-8
[20] => X-FB-Debug: 3lKH0JMHOjd/q5qzs0s6h+WJdk0YnQG67DhnqJa7D3Q=
[21] => Date: Tue, 30 Apr 2013 06:47:00 GMT
[22] => Connection: close
[23] => Content-Length: 0
[24] => HTTP/1.0 200 OK
[25] => Cache-Control: private, no-cache, no-store, must-revalidate
[26] => Expires: Sat, 01 Jan 2000 00:00:00 GMT
[27] => P3P: CP="Facebook does not have a P3P policy. Learn why here: http://fb.me/p3p"
[28] => Pragma: no-cache
[29] => X-Content-Type-Options: nosniff
[30] => X-Frame-Options: DENY
[31] => X-XSS-Protection: 0
[32] => Set-Cookie: datr=5Gh_URQUdhoRh4w74JHDNmtA; expires=Thu, 30-Apr-2015 06:47:00 GMT; path=/; domain=.facebook.com; httponly
[33] => Set-Cookie: reg_ext_ref=deleted; expires=Thu, 01-Jan-1970 00:00:01 GMT; path=/; domain=.facebook.com
[34] => Set-Cookie: reg_fb_gate=http%3A%2F%2Fwww.facebook.com%2Funsupportedbrowser; path=/; domain=.facebook.com
[35] => Set-Cookie: reg_fb_ref=http%3A%2F%2Fwww.facebook.com%2Funsupportedbrowser; path=/; domain=.facebook.com
[36] => Content-Type: text/html; charset=utf-8
[37] => X-FB-Debug: poI8PSRn+KNx3GnMc+8ZcZzsWFncr28gewEWkLisCbc=
[38] => Date: Tue, 30 Apr 2013 06:47:00 GMT
[39] => Connection: close
[40] => Content-Length: 19409
)
Array
(
[0] => HTTP/1.0 302 Found
[1] => Location: https://www.facebook.com/
[2] => Content-Type: text/html; charset=utf-8
[3] => X-FB-Debug: duXMWSWa3Fr5k98z6Ze/HkXeYG5qY8tRuhvCEXg/6wQ=
[4] => Date: Tue, 30 Apr 2013 06:47:00 GMT
[5] => Connection: close
[6] => Content-Length: 0
[7] => HTTP/1.0 302 Found
[8] => Location: http://www.facebook.com/unsupportedbrowser
[9] => P3P: CP="Facebook does not have a P3P policy. Learn why here: http://fb.me/p3p"
[10] => X-Content-Type-Options: nosniff
[11] => Set-Cookie: datr=5Wh_UUqT6BOIQhG3lvSCTnUI; expires=Thu, 30-Apr-2015 06:47:01 GMT; path=/; domain=.facebook.com; httponly
[12] => Content-Type: text/html; charset=utf-8
[13] => X-FB-Debug: B7P9WpeO6QRPr3g+7D/b6w3ssnJMGVa3AXd3qaG6UOA=
[14] => Date: Tue, 30 Apr 2013 06:47:01 GMT
[15] => Connection: close
[16] => Content-Length: 0
[17] => HTTP/1.0 200 OK
[18] => Cache-Control: private, no-cache, no-store, must-revalidate
[19] => Expires: Sat, 01 Jan 2000 00:00:00 GMT
[20] => P3P: CP="Facebook does not have a P3P policy. Learn why here: http://fb.me/p3p"
[21] => Pragma: no-cache
[22] => X-Content-Type-Options: nosniff
[23] => X-Frame-Options: DENY
[24] => X-XSS-Protection: 0
[25] => Set-Cookie: datr=5Wh_Ud4XwmSGX2Uxzg_KAHgW; expires=Thu, 30-Apr-2015 06:47:01 GMT; path=/; domain=.facebook.com; httponly
[26] => Set-Cookie: reg_ext_ref=deleted; expires=Thu, 01-Jan-1970 00:00:01 GMT; path=/; domain=.facebook.com
[27] => Set-Cookie: reg_fb_gate=http%3A%2F%2Fwww.facebook.com%2Funsupportedbrowser; path=/; domain=.facebook.com
[28] => Set-Cookie: reg_fb_ref=http%3A%2F%2Fwww.facebook.com%2Funsupportedbrowser; path=/; domain=.facebook.com
[29] => Content-Type: text/html; charset=utf-8
[30] => X-FB-Debug: 4HXkUp4MHgy+i8qppuZvbHhYH6F4xQlfl0mUNrpj5hY=
[31] => Date: Tue, 30 Apr 2013 06:47:01 GMT
[32] => Connection: close
[33] => Content-Length: 19409
)
4

1 回答 1

1

如果您使用（https://facebook.com/第 1 步）不www带https://www.facebook.com/如果不支持浏览器，它会将您重定向到http://www.facebook.com/unsupportedbrowser（第 4 步）。但是，如果您直接使用https://www.facebook.com/，即从第 2 步开始，它会立即检查您的浏览器（第 3 步），如果不支持，它只会将您重定向到http://www.facebook.com/unsupportedbrowser（第 4 步）。

本页解释 HTTP 状态代码定义

（我记下了我认为是您正在寻找的答案的文字）

http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html

10.3.2 301 永久移动

请求的资源已被分配一个新的永久 URI，并且任何将来对该资源的引用都应该使用返回的 URI 之一。如果可能，具有链接编辑功能的客户端应该自动将对 Request-URI 的引用重新链接到服务器返回的一个或多个新引用。除非另有说明，否则此响应是可缓存的。

新的永久 URI 应该由响应中的 Location 字段给出。除非请求方法是 HEAD，否则响应的实体应该包含一个简短的超文本注释，其中包含指向新 URI 的超链接。

如果收到 301 状态代码以响应 GET 或 HEAD 以外的请求，用户代理不得自动重定向请求，除非用户可以确认，因为这可能会改变发出请求的条件。

  Note: When automatically redirecting a POST request after
  receiving a 301 status code, some existing HTTP/1.0 user agents
  will erroneously change it into a GET request.

10.3.3 302 找到

请求的资源临时驻留在不同的 URI 下。由于重定向有时可能会改变，客户端应该继续使用 Request-URI 来处理未来的请求。此响应仅在由 Cache-Control 或 Expires 标头字段指示时才可缓存。

临时 URI 应该由响应中的 Location 字段给出。除非请求方法是 HEAD，否则响应的实体应该包含一个简短的超文本注释，其中包含指向新 URI 的超链接。

如果收到 302 状态代码以响应 GET 或 HEAD 以外的请求，除非用户可以确认，否则用户代理不得自动重定向请求，因为这可能会改变发出请求的条件。

  Note: RFC 1945 and RFC 2068 specify that the client is not allowed
  to change the method on the redirected request.  However, most
  existing user agent implementations treat 302 as if it were a 303
  response, performing a GET on the Location field-value regardless
  of the original request method. The status codes 303 and 307 have
  been added for servers that wish to make unambiguously clear which
  kind of reaction is expected of the client.
于 2013-04-30T07:13:53.937 回答