[Admin]

You don't need to check the parsed message for [img] code, you can do that right in the source:

    $posts_needed_for_img = 20;
    if($bbuserinfo[posts] < $posts_needed_for_img and strstr($message, '[img]')) {
      eval("standarderror(\"".gettemplate("error_noimagesallowed")."\");");
      exit;
    }