fopen() documentation states that $http_response_header will contain the header entities. It seems to work for most URLs, but is incomplete for others.

Test URL: http://atlas.gc.ca/site/english/index.html

1. test code:
$f=@fopen("http://atlas.gc.ca/site/english/index.html','r');
if($f){
  print_r($http_response_header);
  fclose($f);
}

gives this output:

Array
(
    [0] => HTTP/1.0 200 OK
    [1] => Date: Mon, 26 Aug 2002 15:47:17 GMT
    [2] => Server: Apache/1.3.26 (Unix) mod_fastcgi/2.2.12
    [3] => X-Powered-By: Zope (www.zope.org), Python (www.python.org)
    [4] => Content-Length: 24612
    [5] => Content-Type: text/html
    [6] => X-Cache: MISS from atlas.gc.ca
    [7] => Connection: close
)

2. but lynx -dump -head http://atlas.gc.ca/site/english/index.html

returns a more detailed response:

HTTP/1.0 200 OK
Date: Mon, 26 Aug 2002 15:25:10 GMT
Server: Apache/1.3.26 (Unix) mod_fastcgi/2.2.12
X-Powered-By: Zope (www.zope.org), Python (www.python.org)
*Content-Length: 11331
*Ms-Author-Via: DAV
*Accept-Ranges: none
*ETag: ts20690091.09
*Last-Modified: Fri, 23 Aug 2002 15:49:32 GMT
Content-Type: text/html
X-Cache: MISS from atlas.gc.ca
Connection: close                 

Items marked with * above are either missing or are different than $http_response_header. A clue may be that the "Content-Length" is different, but I don't know why.

In particular, I'm looking for "Last-modified". I can get it with lynx, but not with php.

John A. Grant