checkbox array not updating correct records in mysql/php

i have a form that contains a table which is dynamically created from an mysql query.

Each row contains a persons name and a checkbox. what i am trying to do is have the persons record updated with a 1 if the checkbox is checked or 0 if it is unchecked.

The problem is that when i use the below code, the right number of records are updated but not for the right person. here is the relevant form code:

<?php
while ($row = mysqli_fetch_array($queryresult,MYSQLI_ASSOC)) {
echo '
        <tr>
            <td align="left">'. ucfirst($row['CustNumber']) .'</td>
            <td align="left">'. ucfirst($row['Firstname']) .' '. ucfirst($row['Surname']) .'</td>
            <td align="center">
                <input type="hidden" name="cid[]"  value="'. $row['CustNumber'] .'">
                <input type="hidden" name="cbox[]"  value="">
                <input type="checkbox" name="cbox[]"  value="1">
            </td>   
        </tr>';
}

and here is a simplified processing page:

foreach ($_POST['cid'] as $key=>$custid) {
$check = $_POST['cbox'][$key];
    if ($check == "1") {
        //update customer record with 1 query here
    } 
    else {
        //update customer record with 0 query here
    }
}

can some tell me where i am going wrong? feel like I'm close but cant put it all together.