How to implement the addition and subtraction function of a shopping cart in php

Suppose you are developing an e-commerce website and need to implement the addition and subtraction functions of the shopping cart. If your website is developed based on PHP, the following code example will help you understand how to implement this function.

First, we need to display all selected products and their corresponding quantities on the shopping cart page. We can use an HTML table to accomplish this task. In this table, each row represents a product, including the name, price and quantity of the product, as well as add and subtract buttons.

<table>
  <tr>
    <th>商品</th>
    <th>价格</th>
    <th>数量</th>
    <th>操作</th>
  </tr>
  <?php foreach ($items as $item) { ?>
    <tr>
      <td><?php echo $item[&#39;name&#39;]; ?></td>
      <td><?php echo $item[&#39;price&#39;]; ?></td>
      <td><?php echo $item[&#39;quantity&#39;]; ?></td>
      <td>
        <a href="cart.php?action=remove&id=<?php echo $item[&#39;id&#39;]; ?>">-</a>
        <a href="cart.php?action=add&id=<?php echo $item[&#39;id&#39;]; ?>">+</a>
      </td>
    </tr>
  <?php } ?>
</table>

In the above code example, $items is an array that contains all selected product information. When the page loads, the table content will be dynamically generated based on this array.

On each plus or minus button, we set a link with parameters to tell the PHP script the operation to be performed and the corresponding product ID. For example, when the user clicks the plus button, the browser will send a request similar to the following link to the cart.php page:

cart.php?action=add&id=123

In the PHP script, we can obtain these parameters through the $_GET array, And perform different operations according to different parameter values. The following is a simple PHP script example to implement the shopping cart addition and subtraction functions.

<?php
session_start();

// 加入购物车
function add_to_cart($id) {
  if (!isset($_SESSION[&#39;cart&#39;])) {
    $_SESSION[&#39;cart&#39;] = array();
  }

  if (isset($_SESSION[&#39;cart&#39;][$id])) {
    $_SESSION[&#39;cart&#39;][$id]++;
  } else {
    $_SESSION[&#39;cart&#39;][$id] = 1;
  }
}

// 从购物车中移除商品
function remove_from_cart($id) {
  if (isset($_SESSION[&#39;cart&#39;][$id])) {
    if ($_SESSION[&#39;cart&#39;][$id] > 1) {
      $_SESSION['cart'][$id]--;
    } else {
      unset($_SESSION['cart'][$id]);
    }
  }
}

// 根据ID获取商品信息
function get_item_info($id) {
  // 从数据库或其他资源中获取商品信息
  // 这里简单模拟一下
  $items = array(
    array('id' => 1, 'name' => '商品1', 'price' => 100),
    array('id' => 2, 'name' => '商品2', 'price' => 200),
    array('id' => 3, 'name' => '商品3', 'price' => 300),
  );

  foreach ($items as $item) {
    if ($item['id'] == $id) {
      return $item;
    }
  }

  return null;
}

// 根据购物车中所有商品ID获取商品信息
function get_cart_items_info() {
  $items = array();

  foreach ($_SESSION['cart'] as $id => $quantity) {
    $item = get_item_info($id);

    if ($item) {
      $item['quantity'] = $quantity;
      $items[] = $item;
    }
  }

  return $items;
}

// 处理加减操作
if (isset($_GET['action']) && isset($_GET['id'])) {
  switch ($_GET['action']) {
    case 'add':
      add_to_cart($_GET['id']);
      break;
    case 'remove':
      remove_from_cart($_GET['id']);
      break;
  }
}

// 获取购物车中所有商品信息
$items = get_cart_items_info();
?>

In the above code example, we use Session in PHP to store shopping cart information. When the user clicks the add or subtract button, the PHP code will update the information in the Session based on the corresponding product ID.

The method of obtaining product information, get_item_info(), can obtain product information from the database or other resources. For the convenience of demonstration, we use a simple array to store product information.

Finally, we use the get_cart_items_info() method to obtain all product information in the shopping cart, and render this information into an HTML table again for users to view.

Through the above example, I believe readers have understood how to use PHP to implement the addition and subtraction functions of the shopping cart. Of course, this is only the most basic implementation method. You can further expand and optimize this function according to your own needs and business logic.

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