title: PHP7.1 mcrypt alternative
body: <p>Mcrypt function has been deprecated as of PHP 7.1.0.</p>
  
  <p>My deprecated string encode / decode functions:</p>
  
  <pre><code>$key: secret key
  $str: string
  
  
  $encoded = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, md5($key), $str, MCRYPT_MODE_CBC, md5(md5($key))));
  
  $decoded = rtrim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, md5($key), base64_decode($str), MCRYPT_MODE_CBC, md5(md5($key))), "\0");
  </code></pre>
  
  <p>Can you suggest some alternatives?</p>