สอบถามครับ พยายามส่งค่า radio จาก code แรกไป code ที่สอง แต่ไม่สามารถอ่านได้(ไม่ดึงข้อมูลจาก database ) ทำอย่างไรดีครับ

<?php require_once('control_db/connect.php'); ?>
<?php require_once('control_db/function.php'); ?>
<?php
if (!isset($_POST['submit'])) {
?>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post" enctype="multipart/form-data">
              <table width="743" border="0" cellspacing="0" cellpadding="0">
                <tr>
                  <td><img src="images/newcarspage/images/selectbrand_head.png" alt="" width="743" height="32" /></td>
                </tr>
                <tr>
                  <td height="59" bgcolor="#f5f5f5"><table width="743" border="0" cellspacing="0" cellpadding="0">
                    <tr>
                      <td width="2" height="61"><img src="images/newcarspage/images/lefttopline.gif" alt="" width="2" height="61" /></td>
                      <td width="148" valign="bottom" class="radiobrand">&nbsp;&nbsp;&nbsp;
                        <input type="radio" name="brand" id="radio" value="alfaromeo" />
                        <label for="brand">Alfa Romeo</label></td>
                      <td width="148" class="radiobrand">&nbsp;&nbsp;&nbsp;
                        <input type="radio" name="brand" id="radio12" value="ferrari" />
                        <label for="brand">Ferrari</label></td>
                      <td width="148" class="radiobrand">&nbsp;&nbsp;&nbsp;
                        <input type="radio" name="brand" id="radio22" value="lamborghini" />
                        <label for="brand">Lamborghini</label></td>
                      <td width="148" class="radiobrand">&nbsp;&nbsp;&nbsp;
                        <input type="radio" name="brand" id="radio32" value="mitsuoka" />
                        <label for="brand">Mitsuoka</label></td>
                      <td class="radiobrand">&nbsp;&nbsp;&nbsp;
                        <input type="radio" name="brand" id="radio42" value="skoda" />
                        <label for="brand">Skoda</label></td>
                      <td width="2" align="right" valign="top"><img src="images/newcarspage/images/righttopline.gif" alt="" width="2" height="61" /></td>
                    </tr>
                  </table></td>
                </tr>
                <tr>
                  <td bgcolor="#f5f5f5"><table width="743" border="0" cellspacing="0" cellpadding="0">
                    <tr>
                      <td width="2"><img src="images/newcarspage/images/leftbottomline.gif" alt="" width="2" height="82" /></td>
                      <td><table width="650" border="0" align="center" cellpadding="0" cellspacing="0">
                        <tr>
                          <td width="99" height="46"  align="right" bgcolor="#f5f5f5"><input name="submit" type="submit" class="go" value="GO" /> </td>
                        </tr>
                      </table></td>
                      <td width="2" align="right" valign="top"><img src="images/newcarspage/images/rightbottomline.gif" alt="" width="2" height="82" /></td>
                    </tr>
                  </table></td>
                </tr>
                <tr>
                  <td height="4" valign="top" bgcolor="#f5f5f5"><img src="images/newcarspage/images/bottomline.gif" alt="" width="743" height="4" /></td>
                </tr>
              </table>
            </form>
<?php
}
else {
$linkName ="test/show.php?carid=".$_POST["brand"];
header("Location: /$linkName");
}
?>
Code (PHP)

<table class="content">
      
        <?php
      $carid = $_GET[brand];
      if($carid=="")
      alertgo("Please choose brand","test3.php");
      
      
      $sql = "select * from model 
            inner join brand
            on model.carid = brand.carid
            where model.carid = '$carid'
            and mactive = 1
            and car_active = 1";
   
      $get = "carid=$carid";

   $result = mysql_query($sql);
   $num = mysql_num_rows($result);
   
   for ($i=1; $i<=$num; $i++){
      $row = mysql_fetch_array($result);
?>
    <td><form id="form1" name="form1" method="post" action="">
    <table width="300" border="0" cellpadding="0" cellspacing="0" class="modeltext">
      <tr>
        <td align="center"><a href="pimage/large/<?php echo $row[mimage]?>"     name="model"><img src="mimage/small/<?php echo $row[mimage]?>" border="0"/></a>
       </td>
      </tr>
      <tr>
        <td align="center"><?php echo $row[mname] ?></td>
      </tr>
    </table>
</form></td>
<?php if ($i%3 == 0 ) echo "</tr><tr>"; ?>   
<?php } ?>   
</table>