SQL Update Query doesnt' Update when using Dropdown list - php

Question

I have 2 tables: product (id, name, quantity, c_id) and product_category (cat_id, cat_name).
I have the option to update the existing products. When I change the name and the quantity it works just fine, but when I try to change the product category the c_id doesn't change to the new one.
The code from the update page (update.php):
<?php
include 'database.php';
$id = $_POST['productId'];
$pdo = Database::connect();
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$sql = "SELECT * FROM product where id = ?";
$q = $pdo->prepare($sql);
$q->execute(array($id));
$data = $q->fetch(PDO::FETCH_ASSOC);
$name = $data['name'];
$quantity = $data['quantity'];
Database::disconnect();
?>
<form id="updateFrom" action="update2.php" method="POST">
<table border="1" cellpadding="10">
<tr align='center'>
<td>Name</th>
<td><input name="name" type="text" value="<?php echo $name;?>"/></td>
</tr>
<tr align='center'>
<td>Quantity</th>
<td><input name="quantity" type="text" value="<?php echo $quantity;?>"/></td>
</tr>
<tr align='center'>
<?php $cat = $pdo->query("SELECT c_name, CATEGORY_ID FROM product_category");
?>
//Here the user selects the new category from the dropdown list
<td>Category</th>
<td>
<select name="c_id">
<?php
while ($rows = $cat->fetch(PDO::FETCH_ASSOC))
{
$cat_name = $rows['c_name'];
$cat_id = $rows['CATEGORY_ID'];
echo"<option value='$cat_id'>$cat_name</option>";
}
?>
</select>
</td>
</tr>
</table>
<input type="hidden" id="productId" name="productId" value="<?php echo $id;?>"/>
<button type="submit">update</button>
</form>
</body>
The code which makes the update (update2.php):
<?php
require 'database.php';
$id = null;
if ( !empty($_POST)) {
$id = $_POST['productId'];
$name = $_POST['name'];
$quantity = $_POST['quantity'];
// update data
$pdo = Database::connect();
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$sql = "UPDATE product set name = ?, quantity = ? WHERE id = ?";
$q = $pdo->prepare($sql);
$q->execute(array($name,$quantity,$id));
Database::disconnect();
header("Location: index.php");
}
?>

Answer 1

You need to set the c_id column from $_POST['c_id'].
if ( !empty($_POST)) {
$id = $_POST['productId'];
$name = $_POST['name'];
$quantity = $_POST['quantity'];
$category = $_POST['c_id'];
// update data
$pdo = Database::connect();
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$sql = "UPDATE product set name = ?, quantity = ?, c_id = ? WHERE id = ?";
$q = $pdo->prepare($sql);
$q->execute(array($name,$quantity,$category,$id));
Database::disconnect();
header("Location: index.php");
}
I also suggest that you have the existing category selected by default in the dropdown.
while ($rows = $cat->fetch(PDO::FETCH_ASSOC))
{
$cat_name = $rows['c_name'];
$cat_id = $rows['CATEGORY_ID'];
$selected = $cat_id == $data['c_id'] ? "selected" : "";
echo "<option value='$cat_id' $selected>$cat_name</option>";
}