Cyrill Osterwalder pointed out that sending "" as data in a header is in

internally, your added one will be used instead. If you add a header with no

contents as in 'Accept:' (no data on the right side of the colon), the

internally used header will get disabled. Thus, using this option you can add

new headers, replace internal headers and remove internal headers. The

headers included in the linked list must not be CRLF-terminated, because

curl adds CRLF after each header item. Failure to comply with this will

result in strange bugs because the server will most likely ignore part

of the headers you specified.

The first line in a request (usually containing a GET or POST) is not a header

and cannot be replaced using this option. Only the lines following the

request-line are headers.

new headers, replace internal headers and remove internal headers. To add a

header with no contents, make the contents be two quotes: \&"". The headers

included in the linked list must not be CRLF-terminated, because curl adds

CRLF after each header item. Failure to comply with this will result in

strange bugs because the server will most likely ignore part of the headers

you specified.

The first line in a request (containing the method, usually a GET or POST) is

not a header and cannot be replaced using this option. Only the lines

following the request-line are headers. Adding this method line in this list

of headers will only cause your request to send an invalid header.

Pass a NULL to this to reset back to no custom headers.