ENC key (256 bits)

Dears please i want to know how to encrypt key using this condition

ENCT=1 is the type of encryption used (AES only supported at the moment).
ENC= is the encode parameters string. All parameters that are normally passed in this request are encoded into a single block and passed as a single parameter (ENC).

i want to send key like this:
$key='566F385ASSDDFAAS4506F25596A72656A5265586C484F464F3E3F2F7576298801';

and then produce the encypted key

any help please