Core_HttpIO::send_headers

public static function send_headers()
{
    if (!headers_sent())
    {
        if (isset($_SERVER['SERVER_PROTOCOL']))
        {
            // Use the default server protocol
            $protocol = $_SERVER['SERVER_PROTOCOL'];
        }
        else
        {
            // Default to using newer protocol
            $protocol = 'HTTP/1.1';
        }

        if (HttpIO::$status != 200)
        {
            // HTTP status line
            header($protocol . ' ' . HttpIO::$status . ' ' . HttpIO::$messages[HttpIO::$status]);
        }

        foreach (HttpIO::$headers as $name => $value)
        {
            if (is_string($name))
            {
                // Combine the name and value to make a raw header
                $value = "{$name}: {$value}";
            }

            // Send the raw header
            header($value, true);
        }
    }
}