Using PHP to posting mutiple HTML form fields

Ok, first off, you're not passing the item id into the form so it knows what item to actually update.

Let me see what I can do here:

while ($rows2 = mysql_fetch_array($result2)) 
{
  $id=$rows2['id'];
  $gitem=$rows2['item'];
  $gdesc=$rows2['description'];

  $menu='<input name="qty[' . $id . ']" type="text" class="textfield" id="qty1" value="'. $gitem .'" size="25"/>
          <textarea name="desc[' . $id . ']" cols="10" rows="3" class="textfield" id="desc1" style="width: 222px; height: 51px;">'.$gdesc .'</textarea>';
  echo $menu; 
}

This should return 2 arrays when submitted, qty and desc, with the keys of each entry equal to the id from the DB.

Then when checking the submission:

if($_POST['submit']) //Wanna check this first off, checks whether or not form has been submitted, don't want to do anything at all concerning processing the submission if the form hasn't been sumbitted, probably better to do if(isset($_POST['submit'])) rather than checking directly. 
{
 $qty = $_POST['qty'];  //These two variable declarations assign the two form field arrays into easier to type/identify variable names, might want a little additional error checking to at least make sure that these are arrays with is_array() before going into the foreach loop.
 $desc = $_POST['desc'];

 //Loop through each entry from the form, UPDATE entries in database that correspond to array keys
 foreach($qty as $key => $value)  //Set up a loop on the $qty array from the form as array $key and $value and iterate through each entry in the array, the array keys should be the same item id from the DB that corresponds to both qty and desc value entries
 {
    $sitem = mysql_real_escape_string($value);  //Escape $qty[$key] ($value) textfield input from form, put it in an easy to type variable.  Note also, mysql_real_escape_string requires an active mysql connection to have been previously established elsewhere.  mysql_escape_string() which you were using is depreciated, mysql_real_escape_string() is better.

    $sdesc = mysql_real_escape_string($desc[$key]);  //Escape $desc[$key] textarea input from form, put it in an easy to type variable.  Since the keys should match, you can reach outside the foreach into $desc for it.

    $id = mysql_real_escape_string($key);  //Escape $key (id) from form, in case of malicious live html editing, might be best to cast to (int) instead like $id = (int)$key since id should always be an int.

    $sql = "UPDATE `products` SET `item` = '$sitem', `description` = '$sdesc' WHERE `id` = $id LIMIT 1";  //Construct SQL query from escaped variables.  Backticks around field and table names are pretty standard formal syntax.  LIMIT 1 speeds up the query and reduces db server load because it will stop when it finds a matching WHERE condition rather than continuing to look for more, and there should only be a single matching id field, so no reason to continue to look for more.

    mysql_query($sql);  //Execute Query
 }
}

Oh, here's the code for doing it with PDO for extra security:

if($_POST['submit']) //Wanna check this first off
{
 $qty = $_POST['qty'];
 $desc = $_POST['desc'];

 $dsn="mysql:dbname=whateveryourdbisnamed;host=localhost";  //Of course change values to appropriate ones

 $dbh = new PDO($dsn,"mysqlusername","mysqlpassword");  //Connect to DB.  Might want some error checking to make sure it connected.

 foreach($qty as $key => $value)
 {
    $sql = "UPDATE `products` SET `item` = :item, `description` = :desc WHERE `id` = :id LIMIT 1";

    $stmt = $dbh->prepare($sql);
    $stmt->bindParam(":item",$value,PDO::PARAM_INT); //Note:  Not sure if item is a number of not.  If a string of any length, change it to next line
    //$stmt->bindParam(":item",$value,PDO::PARAM_STR,128);  //Note, change last parameter to set max length of string
    $stmt->bindParam(":desc",$desc[$key],PDO::PARAM_STR,256);  //Change last parameter to set max length of desc, or remove if no max length
    $stmt->bindParam(":id",$key,PDO::PARAM_INT);

    $stmt->execute();  //Execute query
 }
}