php - need assistance with sql injection

First, I'm not trying to hack or do anything illegal. Thought I let you guys know. I have a client that want's me to do some modifications on his system, when I was looking at it I notice that NOTHING was escaped. I'm not joking, nothing is being escaped. I explained to him that it's insecure to have a system like that. He then proceeds to tell me that he's had his system like this for few years and nothing has happened. I need to show him that his system is not safe, but I really don't know to do perform an sql injection. Here's a few queries that use $_GET and are not escaped.

SELECT *,DATE_FORMAT(joined,'%M %d, %Y') as \"Joined\" FROM `members` WHERE `name` LIKE '".$ltr."%' ORDER BY points DESC LIMIT $page,50

Here's another one:

SELECT * FROM groups WHERE id=$thisladder[grid]

The only thing that I see that "might" clean the $_GET is this function:

if (!ini_get('register_globals')) {
   $superglobals = array($_SERVER, $_ENV,
       $_FILES, $_COOKIE, $_POST, $_GET);
   if (isset($_SESSION)) {
       array_unshift($superglobals, $_SESSION);
   }
   foreach ($superglobals as $superglobal) {
       extract($superglobal, EXTR_SKIP);
   }
}

It's possible that the function above may be sanitizing the variables. And yes, the system also uses register globals, which is also bad.

I also made a backup, just in case.