Stuck on php code for the postbit? lol

[HMBeaty]

Ok, I'm a little confused as to why this isn't working. The code works, however, when I try adding in the option so only certain usergroups can('t) view the content, it doesn't work, nothing shows up.

Here's the current code I'm using:
Hook location: postbit_display_start

PHP Code:

$noadsense = explode(',', $vbulletin->options['usml_google_adsense_usergroups']);

if ($this->registry->options['usml_google_adsense_enable'] && is_member_of($vbulletin->userinfo, $noadsense))
{
    if ($this->registry->options['usml_google_adsense_firstpost'] && $post['isfirstshown'])
    {
        $template_hook['postbit_end'] .= '
        <li class="firstpost_advert_container">
            <div class="firstpost_advert">
                '.$this->registry->options[usml_google_adsense_firstpostadcode].'
            </div>
        </li>';
    }
} 


Obviously it's something silly I'm looking over (again ), but what is the problem that

PHP Code:

is_member_of($vbulletin->userinfo, $noadsense) 


doesn't work as it should?