#http\Message http\Message::setHeader(string $header[, mixed $value = NULL])

Set a single header. See http\Message::getHeader() and http\Message::addHeader().

NOTE:
Prior to v2.5.6/v3.1.0 headers with the same name were merged into a single header with values concatenated by comma.

Params:#

• string $header#
  The header's name.
• Optional mixed $value# = NULL
  The header's value. Removes the header if NULL.

Returns:#

• http\Message, self.

Changelog:#

0. v2.5.6, v3.1.0
   • Multiple headers with the same name are kept separate instead of merged together.