It seems that, if the server returns an HTTP/1.1 100 Continue, the variable $http_response_header is unset. This corner case may be difficult to be detected.
For this and other reasons I recommend PHP cURL, instead of file_get_contents().
$http_response_header — HTTP 响应头
$http_response_header 数组与 get_headers() 函数类似。当使用HTTP 包装器时，$http_response_header 将会被 HTTP 响应头信息填充。$http_response_header 将被创建于局部作用域中。
Example #1 $http_response_header 范例
<?php
function get_contents() {
file_get_contents("http://example.com");
var_dump($http_response_header);
}
get_contents();
var_dump($http_response_header);
?>
以上例程的输出类似于：
array(9) {
[0]=>
string(15) "HTTP/1.1 200 OK"
[1]=>
string(35) "Date: Sat, 12 Apr 2008 17:30:38 GMT"
[2]=>
string(29) "Server: Apache/2.2.3 (CentOS)"
[3]=>
string(44) "Last-Modified: Tue, 15 Nov 2005 13:24:10 GMT"
[4]=>
string(27) "ETag: "280100-1b6-80bfd280""
[5]=>
string(20) "Accept-Ranges: bytes"
[6]=>
string(19) "Content-Length: 438"
[7]=>
string(17) "Connection: close"
[8]=>
string(38) "Content-Type: text/html; CHARSET=gb2312"
}
NULL
It seems that, if the server returns an HTTP/1.1 100 Continue, the variable $http_response_header is unset. This corner case may be difficult to be detected.
For this and other reasons I recommend PHP cURL, instead of file_get_contents().
If an HTTP Redirect is encountered, the headers will contain the response line and headers for all requests encountered. Consider this example:
<?php
file_get_contents("https://httpbin.org/redirect-to?url=https%3A%2F%2Fhttpbin.org%2F");
var_dump($http_response_header);
?>
Produces the following:
array(23) {
[0]=>
string(18) "HTTP/1.1 302 FOUND"
[1]=>
string(17) "Connection: close"
[2]=>
string(22) "Server: meinheld/0.6.1"
[3]=>
string(35) "Date: Tue, 06 Feb 2018 11:21:21 GMT"
[4]=>
string(38) "Content-Type: text/html; CHARSET=gb2312"
[5]=>
string(17) "Content-Length: 0"
[6]=>
string(30) "Location: https://httpbin.org/"
[7]=>
string(30) "Access-Control-Allow-Origin: *"
[8]=>
string(38) "Access-Control-Allow-Credentials: true"
[9]=>
string(19) "X-Powered-By: Flask"
[10]=>
string(34) "X-Processed-Time: 0.00107908248901"
[11]=>
string(14) "Via: 1.1 vegur"
[12]=>
string(15) "HTTP/1.1 200 OK"
[13]=>
string(17) "Connection: close"
[14]=>
string(22) "Server: meinheld/0.6.1"
[15]=>
string(35) "Date: Tue, 06 Feb 2018 11:21:21 GMT"
[16]=>
string(38) "Content-Type: text/html; CHARSET=gb2312"
[17]=>
string(21) "Content-Length: 13011"
[18]=>
string(30) "Access-Control-Allow-Origin: *"
[19]=>
string(38) "Access-Control-Allow-Credentials: true"
[20]=>
string(19) "X-Powered-By: Flask"
[21]=>
string(34) "X-Processed-Time: 0.00848388671875"
[22]=>
string(14) "Via: 1.1 vegur"
}
Bear in mind this special variable is somehow protected and not populated in some situation when the peer server close the connection early on (ssl reset)
=> Undefined variable: http_response_header
A code like this one:
$response = @file_get_contents($url);
empty($http_response_header) && $http_response_header = array('HTTP/1.1 400 Bad request');
Will return a cryptic error message:
Fatal error: Call to undefined function array() on line 2
--
Should you want to cope with this situation:
$hdrs = array('HTTP/1.1 400 Bad request');
!empty($htp_response_header) && $hdrs = $http_response_headers;
Now use $hdrs in place of $http_response_header
parser function to get formatted headers (with response code)
<?php
function parseHeaders( $headers )
{
$head = array();
foreach( $headers as $k=>$v )
{
$t = explode( ':', $v, 2 );
if( isset( $t[1] ) )
$head[ trim($t[0]) ] = trim( $t[1] );
else
{
$head[] = $v;
if( preg_match( "#HTTP/[0-9\.]+\s+([0-9]+)#",$v, $out ) )
$head['reponse_code'] = intval($out[1]);
}
}
return $head;
}
print_r(parseHeaders($http_response_header));
/*
Array
(
[0] => HTTP/1.1 200 OK
[reponse_code] => 200
[Date] => Fri, 01 May 2015 12:56:09 GMT
[Server] => Apache
[X-Powered-By] => PHP/5.3.3-7+squeeze18
[Set-Cookie] => PHPSESSID=ng25jekmlipl1smfscq7copdl3; path=/
[Expires] => Thu, 19 Nov 1981 08:52:00 GMT
[Cache-Control] => no-store, no-cache, must-revalidate, post-check=0, pre-check=0
[Pragma] => no-cache
[Vary] => Accept-Encoding
[Content-Length] => 872
[Connection] => close
[Content-Type] => text/html
)
*/
?>
Note that the HTTP wrapper has a hard limit of 1024 characters for the header lines.
Any HTTP header received that is longer than this will be ignored and won't appear in $http_response_header.
The cURL extension doesn't have this limit.
http_fopen_wrapper.c: #define HTTP_HEADER_BLOCK_SIZE 1024