CodeIgniter - form_checkbox and a required check

I have a little checkbox on a signup form im creating which 'must' be checked before the user is allowed to continue ... Im finding it difficult to figure out how to do this with the form_validation functions as well, basically the 'agree to terms and conditions' checkbox MUST be checked in order for the user to continue, if not, an error message displayed, the code i have at the moment is below, if someone could give me a bit of a helping hand that would be great.

Ok, in my view i have the following

$agreeCheck = array( 'name' => 'agreeCheck', 'id' => 'agreeCheck', 'value' => 'agree', 'checked' => set_che开发者_如何学运维ckbox('agreeCheck', 'agree', FALSE));
<?php echo form_checkbox($agreeCheck); ?>

and then in my controller i have the following

$this->form_validation->set_rules('agreeCheck', 'Agree to the Terms and Conditions', 'required');

At the moment, it only remembers the value that was clicked if there is a submission, except if its not checked, it doesnt return anything.

Try this out:

$this->form_validation->set_rules('agreeCheck', 'Agree to the Terms and Conditions', 'required|isset');

Try this out:

$this->form_validation->set_rules('agreeCheck', '...', 'callback_terms_check');

And then set up this method in the controller:

function terms_check() {
    if (isset($_POST['agreeCheck'])) return true;
    $this->form_validation->set_message('terms_check', 'THIS IS SOOOOO REQUIRED, DUDE!');
    return false;
}