Untitled

PHP Error: Undefined index: event_list when I think its already defined.
<?php include('functions.php'); ?>

<?php
 $yr = $_GET['year_list'];
 $evnt = $_GET['event_list'];
?>

<html>
<head>
 <script type="text/javascript" src="myscripts.js"></script>
</head>
<body>
 <div>
  <form name="myform" >
   Select Year: <?php echo hspacer(1); ?>
   <select id="year_list" name="year_list">
   <?php
    for($year = (date('Y') - 100); $year <= (date('Y') + 100); $year++ ) {
     if ($year == date('Y'))  echo "<option value='$year' name='$year' selected='' >" . $year . "</option>";
     else echo "<option value='$year' name='$year' >" . $year . "</option>";
    }
   ?>
   </select>
   <?php echo hspacer(5); ?>
   Select Event:  <?php echo hspacer(1); ?>
   <select id="event_list" name="event_list" >
   <?php
    $events = array("Karate Tournament", "Beauty Pageant", "Film Festival", "Singing Contest", "Wedding");

    foreach($events as $event) echo "<option value='$event' name='$event' >" . $event . "</option>";
   ?>
   </select>
   <?php echo vspacer(2); echo hspacer(22); ?>
   <input type="submit" id="add_description" name="add_description" value="Add Description" onclick=""/>
  </form>
 </div>
</body>
</html>

<?php
 function hspacer($num_of_spaces) {
  $spaces = "";
  if ($num_of_spaces > 0)  for($i=0; $i<$num_of_spaces; $i++ )  $spaces .= "&nbsp;";

  return $spaces;
 }

 function vspacer($num_of_linefeeds) {
  $linefeeds = "";
  if ($num_of_linefeeds > 0)  for($i=0; $i<$num_of_linefeeds; $i++ )  $linefeeds .= "<br />";

  return $linefeeds;
 }
?>

$yr = isset($_GET['year_list']) ? $_GET['year_list'] : null;
$evnt = isset($_GET['event_list']) ? $_GET['event_list'] : null;