PHP - Pass POST variables with header()?
The header function is used to send HTTP response headers back to the user so actually you cannot use it to create request headers :(
One possibility is to use the CURL but I don't think it is worth of what you are doing.
Dan, You could start and store a session in PHP then save the message as a session variable. This saves you from having to transfer the message in an HTTP request.
Manipulating Sessions
//Start the session
session_start();
//Dump your POST variables
$_SESSION['POST'] = $_POST;
//Redirect the user to the next page
header("Location: bar.php");
Now, within bar.php
you can access those POST variables by re-initiating the session.
//Start the session
session_start();
//Access your POST variables
$temp = $_SESSION['POST'];
//Unset the useless session variable
unset($_SESSION['POST']);
To read more about sessions, check out: http://php.net/manual/en/function.session-start.php