how to remove previously set request header referer field from curl handle?

Question

First I initialize curl handle:

$ch = curl_init();

Next I set the url and referer headers:

curl_setopt($ch,CURLOPT_URL,$url);
curl_setopt($ch,CURLOPT_REFERER,$referer);

And finally execute statement:

curl_exec($ch);

Now I can use another url without closing and reopening the handle, so:

curl_setopt($ch,CURLOPT_URL,$another_url);

And here headache begins, because I do not know how to disable referer header that would be send do server, of course I've tried to put false and null into CURLOPT_REFERER but it causes the referer field to be empty, that is a Referer: is still send to the server but with no value (is this even correct with http specs?).

Is there any option to remove header altogether without closing and reinstantiating curl handle ?

I'd like to avoid it because curl keeps a connection open for some time, if I would constantly close the handle while downloading from the same host it could take more time.

Do you have to remove the header entirely? Coudld you not just set it to be the same as the url you're requesting, or the url from the previous request? — Marc B, Nov 14 '11 at 19:37
Yes, I would like to. There could be servers that are very strict what should be in the referer. Until now I haven't encountered any, but I ask in advance. The question is really that if such behavior is correct with regard to http specification ? — rsk82, Nov 14 '11 at 19:46
Some good info @ http://stackoverflow.com/questions/3787002/reusing-the-same-curl-handle-big-performance-increase — Mike Purcell, Nov 14 '11 at 21:11

score 7 · Accepted Answer · answered Nov 14 '11 at 23:16

You can remove completely the referer field, or any other field normally handled by curl, by passing it without anything after ":" to CURLOPT_HTTPHEADER:

curl_setopt($ch, CURLOPT_HTTPHEADER, array("Referer:"));

And it won't appear at all in the header.

http://curl.haxx.se/libcurl/c/curl_easy_setopt.html#CURLOPTHTTPHEADER

score 1 · Answer 2 · answered Nov 14 '11 at 23:11

The Referer header should be either the full URI or a URI relative to one requested:

http://www.w3.org/Protocols/HTTP/HTRQ_Headers.html#z14

It seems like a blank Referer header meets the spec, so you could just:

curl_setopt($ch,CURLOPT_REFERER,'');

The header will still appear, but it will be blank.

how to remove previously set request header referer field from curl handle?

2 Answers2