PHP获取HTTP头信息

• 获取全部（客户端）HTTP请求头信息

    #1
    array apache_request_headers(void)

    #2：通过$_SERVER获取，每个http请求头信息都以"HTTP_"开头在$_SERVER键中
    # 获取if_modified_since的请求信息
    $_SERVER['HTTP_IF_MODIFIED_SINCE']

• 获取服务器响应一个HTTP请求所发送的所有标头

    # url 请求的服务器的URL地址
    # format 0:返回的头部信息以索引数字形式，1:返回头部信息以关联数组形式
    array get_headers(string $url [, int $format = 0 ] )

    #示例
    $head_arr = get_headers("https://www.baidu.com");
    $head_arr_index = get_headers("https://www.baidu.com",1);
    echo "
";
        print_r($head_arr);
        print_r($head_arr_index);
    echo "
";
#输出结果分别为：
#head_arr
Array
(
[0] => HTTP/1.1 200 OK
[1] => Server: bfe/1.0.8.18
[2] => Date: Tue, 25 Apr 2017 02:50:57 GMT
[3] => Content-Type: text/html
[4] => Content-Length: 14720
[5] => Connection: close
[6] => Last-Modified: Tue, 18 Apr 2017 01:09:00 GMT
[7] => Vary: Accept-Encoding
[8] => Set-Cookie: BAIDUID=B4D4AA198C8E598CF3980583DA807FA1:FG=1; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
[9] => Set-Cookie: BIDUPSID=B4D4AA198C8E598CF3980583DA807FA1; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
[10] => Set-Cookie: PSTM=1493088657; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
[11] => P3P: CP=" OTI DSP COR IVA OUR IND COM "
[12] => X-UA-Compatible: IE=Edge,chrome=1
[13] => Pragma: no-cache
[14] => Cache-control: no-cache
[15] => Accept-Ranges: bytes
[16] => Set-Cookie: __bsi=12770957019260228058_00_10_N_N_15_0303_C02F_N_N_N_0; expires=Tue, 25-Apr-17 02:51:02 GMT; domain=www.baidu.com; path=/
)
#head_arr_index
Array
(
[0] => HTTP/1.1 200 OK
[Server] => bfe/1.0.8.18
[Date] => Tue, 25 Apr 2017 02:47:11 GMT
[Content-Type] => text/html
[Content-Length] => 14720
[Connection] => close
[Last-Modified] => Tue, 18 Apr 2017 01:09:00 GMT
[Vary] => Accept-Encoding
[Set-Cookie] => Array
(
[0] => BAIDUID=D0D69F175CC2E4C205E8EA6D1DEAA1BB:FG=1; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
[1] => BIDUPSID=D0D69F175CC2E4C205E8EA6D1DEAA1BB; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
[2] => PSTM=1493088431; expires=Thu, 31-Dec-37 23:55:55 GMT; max-age=2147483647; path=/; domain=.baidu.com
[3] => __bsi=11987508469614704611_00_22_N_N_16_0303_C02F_N_N_N_0; expires=Tue, 25-Apr-17 02:47:16 GMT; domain=www.baidu.com; path=/
)
[P3P] => CP=" OTI DSP COR IVA OUR IND COM "
[X-UA-Compatible] => IE=Edge,chrome=1
[Pragma] => no-cache
[Cache-control] => no-cache
[Accept-Ranges] => bytes
)