title: mcrypt_decrypt(): The IV parameter must be as long as the blocksize
body: <p>I'm trying to encrypt some information in my code, so I searched for a way to do this.
  I found this on php official website:
  <a href="http://www.php.net/manual/vote-note.php?id=107483&amp;page=book.mcrypt&amp;vote=down" rel="nofollow noreferrer">http://www.php.net/manual/vote-note.php?id=107483&amp;page=book.mcrypt&amp;vote=down</a></p>
  
  <p>So, I changed it a little bit and I did this:</p>
  
  <pre><code>class EncrypterDecrypter {
  
  private $SECRET = "xxxxxxxxxxxxxxxxxxxx";
  
  
  function encrypt($decrypted, $salt = 'zzzzzzzzzzzzzzzzzz') {
      $password = $this-&gt;SECRET;
      // Build a 256-bit $key which is a SHA256 hash of $salt and $password.
      $key = hash('SHA256', $salt . $password, true);
      // Build $iv and $iv_base64.  We use a block size of 128 bits (AES compliant) and CBC mode.  (Note: ECB mode is inadequate as IV is not used.)
      srand();
      $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC), MCRYPT_RAND);
      if (strlen($iv_base64 = rtrim(base64_encode($iv), '=')) != 22)
          return false;
      // Encrypt $decrypted and an MD5 of $decrypted using $key.  MD5 is fine to use here because it's just to verify successful decryption.
      $encrypted = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $decrypted . md5($decrypted), MCRYPT_MODE_CBC, $iv));
      // We're done!
      return $iv_base64 . $encrypted;
  }
  
  public function decrypt($encrypted, $salt = 'zzzzzzzzzzzzzzzzzz') {
      $password = $this-&gt;SECRET;
      // Build a 256-bit $key which is a SHA256 hash of $salt and $password.
      $key = hash('SHA256', $salt . $password, true);
      // Retrieve $iv which is the first 22 characters plus ==, base64_decoded.
      $iv = base64_decode(substr($encrypted, 0, 22) . '==');
      // Remove $iv from $encrypted.
      $encrypted = substr($encrypted, 22);
      // Decrypt the data.  rtrim won't corrupt the data because the last 32 characters are the md5 hash; thus any \0 character has to be padding.
      $decrypted = rtrim(
              mcrypt_decrypt(MCRYPT_RIJNDAEL_128,
                      $key, base64_decode($encrypted),
                      MCRYPT_MODE_CBC, $iv),
              "\0\4");
      // Retrieve $hash which is the last 32 characters of $decrypted.
      $hash = substr($decrypted, -32);
      // Remove the last 32 characters from $decrypted.
      $decrypted = substr($decrypted, 0, -32);
      // Integrity check.  If this fails, either the data is corrupted, or the password/salt was incorrect.
      if (md5($decrypted) != $hash)
          return false;
      // Yay!
      return $decrypted;
     }
  }
  </code></pre>
  
  <p>I already tried to change the key and salt size but the warning keeps showing.
  I also searched other topics but I could not find any answer, they all look to specific.</p>