password_verify（）不能使用简单的代码

Here is the code which i have used and similar code used for another login which works perfectly.

$password=$get_data[0]['password'];
$pass=$this->input->post('password');
if (password_verify($pass, $password)) {
$get_data_count=1;
$this->session->set_userdata('user_name',$get_data[0]['contact_name']);
$this->session->set_userdata('user_email',$get_data[0]['contact_email']);
$this->session->set_userdata('user_id',$get_data[0]['id']);
} else {
$get_data_count=0;
}

It never enters in if loop.But for another login section i have used similar code and its work perfectly.And one more thing i have used option like $options = array('cost' => 11); for password hash Please help.