This function is used to add additional HTTP header lines to the server response. The http_header parameter MUST finish with <CR><LF> characters. Warning: Each call of this function cancels the effect of the previous call. In order to add to previously set header lines, use the http_header_get function to retrieve the current headers.
A Content-Type or Media-Type header specified as a part of the headers given with this function will override the default. Otherwise the header lines set using this function add to but do not replace the default response headers. Note that this function cannot set the status line. Use http_request_status for that.