why this code dosen't update the data - php

Question

I can't update the data on this code . it just return to the main page without any update . and i am sure about the connection data on connection file .
and all the column in the data bas is correct
so what is the problem please
<?
include "../include/config.php";
echo "<a href='del_update.php'>Delete</a>"
?>
<div class="articleall">
<?
$id = $_REQUEST['do'];
if($_REQUEST['do'] == 'remove'){
$gid= $_GET['id'] ;
$de = mysql_query("delete from article where id='$gid'");
if($de){
echo "Delete doen";
echo '<meta http-equiv="refresh" content="2; url=del_update.php"/>';
exit ;
}
}
#############################################
if($_REQUEST['do'] == 'update'){
$gid2 = $_GET['id'];
$sel = mysql_query("select * from article where id='$gid2'");
$row2 = mysql_fetch_assoc($sel);
$id2 =$row2['id'];
$name2= $row2['name'];
$auther2= $row2['auther'];
$text2 = $row2['text'];
####################################### post
$postid = $_POST['id'];
$postname = $_POST['name'];
$postauther = $_POST['auther'];
$posttext = $_POST['text'];
if($_POST['del_update']){
if($postname ==''){
echo "it is empty";
echo '<meta http-equiv="refresh" content="2; url=del_update.php"/>';
exit ;
}
else {
$update = mysql_query("update article set
name ='$postname',
auther='$postauther'
where id ='$postid'
");
if(isset($update)){
echo "update done ";
echo '<meta http-equiv="refresh" content="2; url=del_update.php"/>';
exit ;
}
}
}
?>
<form action="del_update.php?do=update" method="post" >
title : <input type="text" class="name" name="name" value="<?=$name2; ?>"></br>
auther : <input type="text" class="name" name="auther" value="<?=$auther2;?>"></br>
date : <input type="text" class="name" name="date" value=""></br>
<input type="hidden" class="name" name="id" value=""></br>
text : <textarea value="" id="elm1" name="elm1" rows="15" cols="80" style="width: 80%">
<? echo $text2; ?>
</textarea>
<input type="submit" class="botton" value="update" name="go"><br>
</form>
<?
}
?>
<?
$query = mysql_query("select * from article order by id desc ");
while ($row = mysql_fetch_assoc($query)
){
$id = $row['id'];
$name = $row['name'];
echo "
<div class='shortarticle'>
<h3>$name ||
<a href='?do=remove&id=$id'>Delete</a>||
<a href='?do=update&id=$id'>Update</a>
</h3>
</div>
</div> ";
}
?>