$http_response_header

HTTP 响应头

说明

$http_response_header数组与get_headers()函数类似。当使用HTTP 包装器时，$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。

范例

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=UTF-8"
}
NULL

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

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=utf-8"
 [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=utf-8"
 [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"
}

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
)
*/
?>

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