php - How to depend length of Rijndael function output from input length? -

i have function:

function aes_encrypt($value, $key) {     return base64_encode(security::rijndael($value, $key, 'encrypt')); } 

security::rijndael cakephp security component, implement rijndael 256-bit key encryption.

i've store encrypted data in database, need know how depend length of output input.