I can't see 'on' in url

I am trying to fetch elements which are checked so that I can delete them from database .

I used 'get' method so that I could see elements those I am selecting .

 []21 food
 []22 eggs
 []23 bread
 []24 bread
    

this is my data in database if I am selecting food it is showing

  http://localhost/shopping/delete.php?21=&delete=     (in url) 
    

it should be 21='on', but it is not showing why and please tell me how to fetch them to delete if I cannot do like this .

        <?php require_once("dbconnect.php") ?>
        <?php
        db();
        global $link;
        $query="SELECT * FROM items";
        $result=mysqli_query($link,$query);
        ?>
          <form  action="delete.php" method="get">
            <?php
        while ($arr=mysqli_fetch_array($result)) {
          ?>
    
    
    
      <ul>
        <li> <input type="checkbox" name="<?php echo $arr['id'] ?>" value=""> <?php echo $arr['id'] ?> <?php echo $arr['itemname'] ?> </li>
      
      </ul>
      <?php
       }
       ?>
    
      <button type="submit" name="delete">delete</button>
      </form>