int mcrypt_enc_get_iv_size(resource $td)
This function has been DEPRECATED as of PHP 7.1.0. Relying on this function is highly discouraged.
This function returns the size of the IV of the algorithm specified by the encryption descriptor in bytes. An IV is used in cbc, cfb and ofb modes, and in some algorithms in stream mode.
Returns the size of the IV, or 0 if the IV is ignored by the algorithm.
- resource $td: The encryption descriptor.