How to implement a simple online ordering system using PHP

Today, we will implement a simple online ordering system using the PHP programming language. PHP is a popular server-side scripting language that is ideal for developing web-based applications. We'll show you how to use PHP to create a simple ordering system where users can select items on the website, add them to their shopping cart, and complete the transaction.

Before we begin, we need to create a new PHP project and install the necessary dependencies such as database and server environment. We will be using MySQL as our database, therefore, we need to create a new MySQL database and create a table called "orders". This table will contain the following columns:

• id: an automatically generated unique identifier used to distinguish different orders
• name: the name of the orderer
• address : The address of the orderer
• items: The items ordered, stored in JSON format

Now we can start writing our code. I'll provide some code and explain what they do.

1. Database Connection

We first need to connect to our MySQL database. This can be done using the mysqli function provided by PHP.

$servername = "localhost";
$username = "root";
$password = "";
$dbname = "orders";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接是否成功
if ($conn->connect_error) {
  die("Connection failed: " . $conn->connect_error);
}

2. Getting the menu

Now we need to get the menu from our database. We will create a function called "get_menu" which will get all available menus from the database.

function get_menu($conn) {
  $sql = "SELECT * FROM menu";
  $result = $conn->query($sql);

  if ($result->num_rows > 0) {
    $menu = array();

    // 将结果转换为数组
    while($row = $result->fetch_assoc()) {
      array_push($menu, $row);
    }

    return json_encode($menu);
  } else {
    return "0 结果";
  }
}

3. Add item to cart

We also need a function to allow the user to add items to their cart. This can be achieved by using a function called "add_to_cart". This function will accept the item ID and quantity as parameters and add them to the user's shopping cart.

function add_to_cart($id, $quantity) {
  // 检查物品是否已存在于购物车中
  if(isset($_SESSION["cart"][$id])) {
    $_SESSION["cart"][$id] += $quantity;
  } else {
    $_SESSION["cart"][$id] = $quantity;
  }
}

4. Display Shopping Cart

Now, we are going to create a function that displays the user’s shopping cart. This function will return an HTML table that includes the selected items, their price, quantity, and total price.

function display_cart() {
  $output = "";

  if(!empty($_SESSION["cart"])) {
    $total = 0;

    $output .= "<table>";
    $output .= "<tr><th>物品</th><th>数量</th><th>价格</th><th>总价</th></tr>";

    // 遍历购物车中的每个物品
    foreach($_SESSION["cart"] as $id => $quantity) {
      $sql = "SELECT name, price FROM menu WHERE id = $id";
      $result = $conn->query($sql);

      if ($result->num_rows > 0) {
        $row = $result->fetch_assoc();

        $name = $row["name"];
        $price = $row["price"];
        $total_price = $price * $quantity;
        $total += $total_price;

        $output .= "<tr><td>$name</td><td>$quantity</td><td>$price 元</td><td>$total_price 元</td></tr>";
      }
    }

    $output .= "<tr><td colspan='3'>总价</td><td>$total 元</td></tr>";
    $output .= "</table>";
  } else {
    $output .= "购物车为空";
  }

  return $output;
}

5. Submit order

Finally, we need a function to handle user submitted orders and save them to our database. This can be achieved by using a function called "submit_order". This function will get all the items from the shopping cart and save them into the "orders" table.

function submit_order($name, $address) {
  $items = json_encode($_SESSION["cart"]);

  // 将订单插入到数据库
  $sql = "INSERT INTO orders (name, address, items)
  VALUES ('$name', '$address', '$items')";

  if ($conn->query($sql) === TRUE) {
    // 清空购物车
    $_SESSION["cart"] = array();

    return true;
  } else {
    return false;
  }
}

Now that we have all the code completed, we can put it all together and create a simple web page. Users can select dishes on the page, add items to their shopping cart, and finally submit their order.

It’s really easy to implement a simple online ordering system in PHP and only requires a few simple functions. Now you can extend this a bit, such as adding functionality that takes price into account or integrating with payment services.

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