        $data .= '<input type="hidden" name="'.htmlspecialchars($key).'" value="'.htmlspecialchars($value).'" />';
    }
    echo "<html><head><title>CSRF check failed</title></head>
        <body>
        <p>CSRF check failed. Your form session may have expired, or you may not have
        cookies enabled.</p>
        <form method='post' action=''>$data<input type='submit' value='Try again' /></form>
        <p>Debug: $tokens</p></body></html>
";
}
The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request.