Update operation in wordpress custom plugin

When we retrieve the data from the database, we have created two (2) buttons in the actions column. One of them is the update button that acts as an anchor tag.

edit.php

<?php

global $wpdb;
$id = $_GET['id'];

$result = $wpdb->get_results("SELECT * FROM wp_customers WHERE id=$id");
foreach ($result as $key => $print) { 
  $name = $print->name;
  $phone = $print->phone;
}

?>

<div class="container card content-center">
<centers>

<div class="card" style="padding:10px; background:white">
<form action="admin.php?page=update-customers" class="" method="post">
<h4>Update Records</h4> 
<div class="mb-3 mt-3">
<label for="uname" class="form-label">Name:</label>
<input type="hidden" name="id" value="<?php echo $id; ?>">
<input type="text" class="form-control" id="unames" placeholder="Enter name" name="name"
value="<?php echo $name; ?>" required>
</div>
<div class="mb-3">
<label for="pwd" class="form-label">Mobile No:</label>
<input type="number" class="form-control" id="number" placeholder="Enter your number" name="mobile"
value="<?php echo $phone; ?>" required>
</div>

<button type="submit" class="btn btn-primary">Submit</button>
</form>

</div>

</centers>
</div>

update.php

   <?php

   global $wpdb;   
   $id = $_POST['id'];
   $name = $_POST['name'];
   $phone = $_POST['mobile'];

   $q = $wpdb->query("UPDATE wp_customers SET name='$name',
     phone='$phone' WHERE id='$id'");

   if($q){ ?>
      <script> window.location.href ="admin.php?page=edit-customers&&id=<?php echo $id; ?>";</script>
     <?php } 
     else{
       echo 'error';
     }

 ?>