使用php更新sql中的特定行

Question

I want to grab the specific $key and $id and insert it into my sql table, How can i get the $key and $id? If i just had 1 row, i could have solve it, but since its a while loop, do i have to do it other way?

I've tried with key as a start like this

if(isset($_POST['$key'])) 

When i press my button for update

if(isset($_POST['$key'])) {
            $dbhost = '*****';
            $dbuser = '*****';
            $dbpass = '*****';

        $conn = db2_connect($dbhost, $dbuser, $dbpass);

        if(! $conn ) {
           die('Could not connect: ');
        }

        $postkey = $_POST['$key'];

        $sql = "UPDATE Products SET , KEY = $key, ID = $ID, DONE = 'X'  " ;
        $retval =  db2_exec( $conn, $sql);

        if(! $retval ) {
          die('Could not update data: ' . db2_stmt_errormsg());
        }
        echo "Updated data successfully
";
        db2_close($conn); 
     }     

Looping my tables

  while((db2_fetch_row($queryexe)){
     $key = db2_result($queryexe, 'KEY');
     $id = db2_result($queryexe, 'ID');
     $done = db2_result($queryexe, 'DONE');

    print("<td>$key</td>
");
    print("<td>$id</td>
");
    print("<td><button  name = '$key' type='submit' id = '$key' class='btn btn-default'>
    <i class='glyphicon glyphicon-repeat'></i> Done
    </button></td>
");
    print("</tr>
");

Sorry if im unclear. I've tried my best