Output encryption library

Hi
I use below code for encryption in my app

PHP Code:

$this->load->library('encryption');
$this->encryption->initialize(array('cipher' => 'aes-256','mode' => 'cbc','key' => 'abcdefgh01234567abcdefgh01234567'));
echo $this->encryption->encrypt('omid'); 


What is encrypt result type?(base64 or hex or other)

Because when i try to decrypt it in android or ios,have an error