Legosp sort products

<?php
$dsn = "mysql:host=localhost;dbname=armmoney_new;charset=utf8";
$opt = array(
    PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC
);
$pdo = new PDO($dsn, 'root', '123456', $opt); // Объект PDO

if($_POST)
{
           $id = $_POST['id'];
           $type = $_POST['type'];
           if($type == 1)
           {
               // to up
               $prewStmt = $pdo->prepare("SELECT * FROM products WHERE sort_by < :sort ORDER by sort_by DESC LIMIT 0,1");
               $prewStmt->execute(['sort' => $current['sort_by']]);
               $prew = $prewStmt->fetch(\PDO::FETCH_ASSOC);

              // var_dump($prew['id'].'-'.$current['id']);die();

               $pdo->exec("UPDATE products SET sort_by=".$prew['sort_by']." WHERE id=".$current['id']);
               $pdo->exec("UPDATE products SET sort_by=".$current['sort_by']." WHERE id=".$prew['id']);
           }else{
               // to down
               $nextStmt = $pdo->prepare("SELECT * FROM products WHERE sort_by > :sort ORDER by sort_by ASC LIMIT 0,1");
               $nextStmt->execute(['sort' => $current['sort_by']]);
               $next = $nextStmt->fetch(\PDO::FETCH_ASSOC);

               $pdo->exec("UPDATE products SET sort_by=".$next['sort_by']." WHERE id=".$current['id']);
               $pdo->exec("UPDATE products SET sort_by=".$current['sort_by']." WHERE id=".$next['id']);
           }

           $all = $pdo->prepare("SELECT * FROM `products` ORDER by sort_by ASC");
           $all->execute();
           echo json_encode($all->fetchAll(\PDO::FETCH_ASSOC));die();
}
$stmt = $pdo->prepare("SELECT * FROM `products` ORDER by sort_by ASC");
$stmt->execute();
$data = $stmt->fetchAll(PDO::FETCH_ASSOC);
?>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>

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<table class="table">
    <thead>
    <tr>
        <th>ID</th>
        <th>NAME</th>
        <th></th>
    </tr>
    </thead>
    <tbody id="tb">
    <?php foreach($data as $d) { ?>
    <tr>
        <td><?=$d['id']?></td>
        <td><?=$d['name']?></td>
        <td>
            <button class="btn btn-success btn-sm" onclick="up(<?=$d['id']?>)">To UP</button>
            <button class="btn btn-danger btn-sm" onclick="down(<?=$d['id']?>)">To Down</button>
        </td>
    </tr>
    <?php } ?>
    </tbody>
</table>

<script>
    function up(id) {
        $.post('/', {id:id, type: 1}, function(data){
            var d = JSON.parse(data);
            $("#tb tr").remove();
            $.each(d, function (k, v) {
                $("#tb").append('<tr>' +
                    '<td>'+v.id+'</td>' +
                    '<td>'+v.name+'</td>' +
                    '<td>'+
                    '<button class="btn btn-success btn-sm" onclick="up('+v.id+')">To UP</button>' +
                    '<button class="btn btn-danger btn-sm" onclick="down('+v.id+')">To Down</button>' +
                '</td>'+
                '</tr>');
            });
        })
    }
    function down(id) {
        $.post('/', {id:id, type: 0}, function (data) {
            var d = JSON.parse(data);
            $("#tb tr").remove();
            $.each(d, function (k, v) {
                $("#tb").append('<tr>' +
                    '<td>'+v.id+'</td>' +
                    '<td>'+v.name+'</td>' +
                    '<td>'+
                    '<button class="btn btn-success btn-sm" onclick="up('+v.id+')">To UP</button>' +
                    '<button class="btn btn-danger btn-sm" onclick="down('+v.id+')">To Down</button>' +
                    '</td>'+
                    '</tr>');
            });

        })
    }
</script>