string
$name, mixed
$value)Add an header, appending to already existing headers. See http\Message::addHeaders() and http\Message::setHeader().
<?php
$msg = new http\Message;
$msg->addHeader("X-Num", "123");
$msg->addHeader("X-Num", "456");
echo $msg;
?>
Yields:
X-Num: 123, 456