如何更改表单以便仅发布选定的字段

I have a form automatically generated from a mysql query with all the books available to be ordered for our bookstore. The problem is that ISBNs for all books available are posted instead of only the ones that we've selected, and that wastes a lot of memory.

Is it possible to only post the data that we've selected or does every input field within the brackets have to be posted?

Here's what the form looks like:

<form name="form" action="postdata.php" method="post">
<?php
$k=0;    
while ($books = mysqli_fetch_array($booksq)){
   $bookISBN[$k]=$books['theISBN'];
   echo '<textarea name="'.$bookISBN[$k].'"></textarea>'.$bookISBN[$k].'<br>;
   $k+=1;
   }
?>
</form>

Using that form we select which books we want to order and enter the quantity we want in the text area.

Here's what the $_POST data looks like with a few books selected:

  [9780872865082]=>
  string(0) ""
  [9780872865198]=>
  string(1) "1"
  [9780872865709]=>
  string(0) ""
  [9780872866294]=>
  string(1) "1"
  [9780912678764]=>
  string(0) ""
  [9780930324872]=>
  string(1) "1"
  [9780941920056]=>
  string(0) ""
  [9780971084636]=>
  string(0) ""
  [9780975571644]=>
  string(0) ""
  [9781553800439]=>
  string(0) ""
  [9781556591075]=>
  string(0) ""
  [9781566892759]=>
  string(0) ""
  [9781570270871]=>
  string(0) ""
  [9781617753121]=>
  string(0) ""

How do I change my form so data only posts when string(1) "1"?

Maybe something like this:

while ($books = mysqli_fetch_array($booksq)){
    $bookISBN[$k]=$books['theISBN'];
    if ($Count == 1) {
        echo '<textarea name="'.$bookISBN[$k].'">'.$Count.'</textarea> ';
    }
}

My solution to this was to use javascript to separate the ISBNs that we want to order into one field that can then be posted.

<script type="text/javascript">
    function updatesum() {
      var m=0, ISBN, order, list=[], count=<?php echo $k; ?>-1, quant;
          while (m <= count) {
            tmp = 'n'+m;
            quant = (Number(document.getElementById(tmp).value));
            ISBN = (Number(document.getElementById(tmp).name));
            order = quant+'.'+ISBN;
            if (quant>0) {list.push(order);}
            m++;
          }

      document.getElementById('list').value = list;
    }    

</script>