PHP Notice: String offset cast occurred in /var/www/file.php on line 16
$c3_key = base64_encode(sha1(md5($c_key) . md5($c2_key)));
$mid = round($last / 2);
16 ----$c3_key = substr($c3_key, 1, round(ord($ckey[$mid]) / 9));
$c_key = $c_key . $c2_key . $c3_key;