如何使用mcrypt_decrypt（）的openssl_decrypt（）

I have a string which is perfectly decrypted using:

mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $encrypted, MCRYPT_MODE_CBC, $iv)

Now, I have to decrypt data using the openssl_decrypt() function.

I tried using:

openssl_decrypt ($encrypted, 'AES-256-CBC', $key , 0 , $iv);

But, I got:

RESULT = <blank>