How to get value of an input if checkbox in that row is clicked in PHP

Question

In my code I have it so that it will show a row with mysql and at the end I have an input to put in a date and then insert it into the database. I cannot figure out how to make it so that it updates each input individually with each checked box row.

$i = 0;
while($row = $result->fetch_assoc()) {
   echo  "<div class='row'>
    <div class='col-md-10 col-offset-1'>
    <tr>
    <td>
    <input type='checkbox' name='chk1[$i]' value='".$row['customerid']."' /> " .$row['firstname']." ".$row['lastname']. 
    "</td>
    <td>"  .
    $row['phonenumber'].
    "</td> 
    <td>" .$row['brand'].
    "</td>
    <td>" .$row['stock'].
    "</td>
    <td>" .$row['shoename'].
    "</td>
    <td>" .$row['size'].$row['width']. "</td>"; 
    echo "<td><input name='backorder' type='date'/></td>
    <td id='comments'>" .$row['comment']. "</td> 
    </div>
    </div>";
$cid[$i] = $row['customerid'];
$i++;
}

So when I update with this below it updates everything fine but gives all rows in the database the same value for the backorder.

if(isset($_POST['chk1'])) {
    foreach($_POST['chk1'] as $cid[$i]) {
        $chk1[] = array($cid[$i]);
        if(!empty($chk1)) {

            //include("email.php");
            $sql = "SELECT * FROM shoes WHERE customerid =" .$cid[$i];
            $result = $conn->query($sql);

            if ($result->num_rows > 0) {
                // output data of each row
                while($row = $result->fetch_assoc()) {
                    $texting = $row['texting'];
                    $name = $row['firstname'];
                    $email = $row['email'];
                    $provider = $row['provider'];
                    $brand = $row['brand'];
                    //$sql must be in this loop in order to execute all checkboxes.

                    $sql = "UPDATE shoes SET ordered=CURDATE(), backorder='backorder' WHERE customerid=".$cid[$i];

Answer 1

Your SQL sends a static string value for the update of that field.

$sql = "UPDATE shoes SET ordered=CURDATE(), backorder='backorder' WHERE customerid=".$cid[$i]; Needs to be updated to use something variable for the value or the string "backorder" will become the value for anything updated.