Undefined index

Hej jeg har brug for lidt hjælp.
Jeg har lavet en side der driller mig lidt, Her er koden

?PHP
$db = new DB2(); 
$form = new Form();
$db->connect("localhost", "xxxx", "xxxx");
$db->SelectDb("xxxxx");
if(isset($_POST['submit']))
    {
        $db->CreateWorkshop();
        echo "db";
    }
define('link','start');
   
?>

<?php
if($_GET['link'] == "CreateWorkshop")&#61663;- LINE 26
{
?>
<form method="post" name="CreateWorkshop" action="<?PHP $_SERVER['PHP_SELF']; ?>">
<table>
    <tr><td>
            Workshop name
        </td><td>
            <?PHP echo $form->Input("name"); ?>
        </td></tr><tr>
        <td>
            Workshop start
        </td><td>
            <?PHP echo $form->Date("Start");?>
        </td></tr><tr><td>
            Workshop end
        </td><td>
            <?PHP echo $form->Date("end");?>
        </td></tr><tr><td>
            Max lead
        </td><td>
            <?PHP echo $form->Input("maxlead");?>
        </td></tr><tr><td>
            Max fallow
        </td><td>
            <?PHP echo $form->Input("maxfallow");?>
        </td></tr><tr>
        <td colspan="2">
            <?php echo $form->Submit("submit","Create");?>
        </td></tr>
</table>
</form>
<?php
}
?>

Jeg for denne fejl når jeg prøver at køre siden
Notice: Undefined index: link in C:\Program Files\Apache Software Foundation\Apache2.2\htdocs\test\index.php on line 26