Request.php
public static function sendHeaders(): void
    {
        if (!(SOCKET || headers_sent())) {
            if (isset($_SESSION['Cookies']) && \is_array($_SESSION['Cookies'])) {
                foreach ($_SESSION['Cookies'] as $key => $array) {
                    if ($array[1] ?? false) {
                        static::setCookie($key, $array[0] ?? null, $array[1]);
                    } else {
                        static::setCookie($key, $array[0] ?? null);
                    }
                }
            }

            if (isset($_SESSION['Headers']) && \is_array($_SESSION['Headers'])) {
                foreach ($_SESSION['Headers'] as $value) {
                    static::setHeader($value);
                }
            }
            unset($_SESSION['Cookies'], $_SESSION['Headers']);
        }
    }
public static function sendHeaders(): void
    {
        if (!(SOCKET || headers_sent())) {
            if (isset($_SESSION['Cookies']) && \is_array($_SESSION['Cookies'])) {
                foreach ($_SESSION['Cookies'] as $key => $array) {
                    if ($array[1] ?? false) {
                        static::setCookie($key, $array[0] ?? null, $array[1]);
                    } else {
                        static::setCookie($key, $array[0] ?? null);
                    }
                }
            }

            if (isset($_SESSION['Headers']) && \is_array($_SESSION['Headers'])) {
                foreach ($_SESSION['Headers'] as $value) {
                    static::setHeader($value);
                }
            }
            unset($_SESSION['Cookies'], $_SESSION['Headers']);
        }
    }
Headers can only be sent and set if output has not already started.
If we attempt to set a header after output has started, store it and
send on the next request.
@return void