session ไม่ Clear เวลาเปิดหน้า ไว้นานๆ หรือปิด ie ครับ รบกวนผู้รู้ช่วยทีครับ

<?php
session_start();  
?>
<?php
mysql_connect("localhost","root","root");
mysql_select_db("epr2");
$strSQL = "SELECT * FROM product";
$objQuery = mysql_query($strSQL)  or die(mysql_error());
?>

  <tr>
    <td height="133" valign="top" bgcolor="#00CCFF"><table width="1065" height="480" border="0" align="left">
      <tr>
        
        <td width="1059" rowspan="10" align="left" valign="top" bgcolor="#FFFFFF"><table width="910" border="0"bordercolor="#66CC66"bgcolor="#FFFFFF">
  <tr>
    <td width="900" height="107"><form name="frmSearch" method="get" action="<?php echo $_SERVER['SCRIPT_NAME'];?>">
 <center> <table width="599" border="1">
    <tr>
      <th>Keyword
      <input name="txtKeyword" type="text" id="txtKeyword" value="<?php echo $_GET["txtKeyword"];?>">
      <input type="submit" value="Search"></th>
    </tr>
  </table><BR>
  <?php
if($_GET["txtKeyword"] != "001")
	{
	$objConnect = mysql_connect("localhost","root","root") or die("Error Connect to Database");
	$objDB = mysql_select_db("epr2");
	// Search By Name or Email
	$strSQL = "SELECT * FROM product WHERE (id_prd LIKE '%".$_GET["txtKeyword"]."%' or ProductName LIKE '%".$_GET["txtKeyword"]."%' )";
	$objQuery = mysql_query($strSQL) or die ("Error Query [".$strSQL."]");
	?>
</form>
      <?php