issue with checkbox on update

Hi I just found an odd issue. I have an update page with some checkboxes, after some testing I found that some checkboxes were able to update in the database and some did not. This confused me as its the same syntax of code. After looking at my database, and another test I found that removing Default -> As defined: 1 this solved the issue.For example look at the screenshot before the fix. I don't understand this as I assumed the Default in phpMyAdmin was only in case there was NULL in the table field?

Here is the php code on my page to show its correct.

$UpdateQuery->bindColumn("ProductNewArrival", "c", "".((isset($_POST["newarrival"]))?$_POST["newarrival"]:"")  ."", "WA_DEFAULT");

<input <?php if (!(strcmp(($rsProduct->getColumnVal("ProductNewArrival")),1))) {echo "checked=\"checked\"";} ?> name="newarrival" type="checkbox">

I wanted to use the Default: as defined in phpMyAdmin so that I can ensure a value is set. What am I misunderstanding? because it seems that if Default: as defined is set to 0 in phpMyAdmin it works fine. but if I use a value of 1 it doesn't allow my php update page to update the database?

Chris