get number of elements in POST

I have a page where a user will be entering numbers into text boxes. The number of textboxes will vary, and I need to update a database with the values entered in these boxes.

So is there a way to determine how many values are being passed in the POST method?

something like:

PHP Code:

---

While($check==1)
{
$box=databox$i;
if($_POST[$box]!="")
{
 /// run SQL query to update DB for that value
}
else
  check=0;
$i++;
} 


---

Something close to that... !?

Something like this will loop $_POST:

Code:

---

foreach ($_POST as $key => $value) {
  echo "$_POST['$key'] = $value<br />";
}

---

If you give the textboxes in the form names like
<input type="text" name="txtbox[0]" />
you can retrieve the count of them in PHP with a simple

Code:

---

<?php echo count($_POST['txtbox']); ?>

---