Multi user marketplace

To create this marketplace with multi-user authentication in PHP, you'll need to build several key components:

1. User Authentication

Registration and Login:
- Create a registration system where users sign up with their email and password.
- Implement a login system with proper password hashing (e.g., using password_hash() and password_verify() in PHP).
Session Management:
- Use PHP sessions to keep users logged in and maintain their state across pages.

2. Database Design

Users Table:
- Columns: id, username, email, password, balance.
Items Table:
- Columns: id, user_id (FK to Users table), title, description, price, category, created_at.
Categories Table:
- Columns: id, name, user_id (FK to Users table), created_at.
Transactions Table:
- Columns: id, buyer_id (FK to Users table), seller_id (FK to Users table), item_id (FK to Items table), amount, transaction_date.

3. User Balance Management

Function to Update Balance:
- Create a PHP function to update the user's balance based on external transactions or actions (e.g., updateBalance($userId, $amount)).
Payment from Balance:
- Deduct the item cost from the buyer’s balance and credit the seller’s balance.

4. Listing Items

Item Creation:
- Allow users to create listings by providing a title, description, price, and a category.
- Users can create custom categories if desired.
Listing Display:
- Display listed items with their categories, seller information, and price.
- Implement search and filter functionality by categories.

5. Purchasing Items

Transaction Process:
- When a buyer purchases an item, deduct the item price from their balance, add it to the seller’s balance, and create a record in the Transactions table.

6. Admin Panel (Optional)

Category Management:
- Admins can manage categories (create, edit, delete) to keep the marketplace organized.

7. Security Considerations

Input Validation:
- Validate and sanitize all user inputs to prevent SQL injection and XSS attacks.
Secure Passwords:
- Use strong hashing algorithms and secure session management.

8. Code Snippets:

User Registration:

// Register new user
function registerUser($username, $email, $password) {
    $hashedPassword = password_hash($password, PASSWORD_BCRYPT);
    $query = "INSERT INTO users (username, email, password, balance) VALUES (?, ?, ?, 0)";
    // Execute query with prepared statements
}

Balance Update:

function updateBalance($userId, $amount) {
    $query = "UPDATE users SET balance = balance + ? WHERE id = ?";
    // Execute query with prepared statements
}

Create Listing:

function createListing($userId, $title, $description, $price, $category) {
    $query = "INSERT INTO items (user_id, title, description, price, category, created_at) VALUES (?, ?, ?, ?, ?, NOW())";
    // Execute query with prepared statements
}

Purchase Item:

function purchaseItem($buyerId, $itemId) {
    // Get item price and seller information
    $item = getItemById($itemId);
    $price = $item['price'];
    $sellerId = $item['user_id'];

    // Begin transaction
    startTransaction();

    // Deduct from buyer's balance
    updateBalance($buyerId, -$price);

    // Credit to seller's balance
    updateBalance($sellerId, $price);

    // Record transaction
    recordTransaction($buyerId, $sellerId, $itemId, $price);

    // Commit transaction
    commitTransaction();
}

This approach covers the basic requirements of your marketplace. Depending on your needs, you may want to add more features like order tracking, messaging between users, or a rating system.

To integrate MySQL with your PHP-based marketplace, you'll need to set up a MySQL database, connect to it using PHP, and execute SQL queries for user authentication, item management, and transaction handling. Below is a step-by-step guide on how to integrate MySQL into your PHP marketplace:

1. Set Up MySQL Database

Create a MySQL Database:
```
CREATE DATABASE marketplace_db;
```

Create Tables:

USE marketplace_db;

-- Users Table
CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) NOT NULL UNIQUE,
    password VARCHAR(255) NOT NULL,
    balance DECIMAL(10, 2) DEFAULT 0.00
);

-- Items Table
CREATE TABLE items (
    id INT AUTO_INCREMENT PRIMARY KEY,
    user_id INT,
    title VARCHAR(100) NOT NULL,
    description TEXT NOT NULL,
    price DECIMAL(10, 2) NOT NULL,
    category VARCHAR(50) NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    FOREIGN KEY (user_id) REFERENCES users(id)
);

-- Categories Table
CREATE TABLE categories (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(50) NOT NULL,
    user_id INT,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    FOREIGN KEY (user_id) REFERENCES users(id)
);

-- Transactions Table
CREATE TABLE transactions (
    id INT AUTO_INCREMENT PRIMARY KEY,
    buyer_id INT,
    seller_id INT,
    item_id INT,
    amount DECIMAL(10, 2) NOT NULL,
    transaction_date TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    FOREIGN KEY (buyer_id) REFERENCES users(id),
    FOREIGN KEY (seller_id) REFERENCES users(id),
    FOREIGN KEY (item_id) REFERENCES items(id)
);

2. Connect PHP to MySQL

Database Connection Script (db.php):

<?php
$host = 'localhost';
$db = 'marketplace_db';
$user = 'root';  // Replace with your MySQL username
$pass = '';      // Replace with your MySQL password

try {
    $pdo = new PDO("mysql:host=$host;dbname=$db;charset=utf8", $user, $pass);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
    die("Could not connect to the database: " . $e->getMessage());
}
?>

3. User Registration Example

Register User (register.php):

<?php
require 'db.php';

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $username = $_POST['username'];
    $email = $_POST['email'];
    $password = $_POST['password'];
    $hashedPassword = password_hash($password, PASSWORD_BCRYPT);

    $stmt = $pdo->prepare("INSERT INTO users (username, email, password) VALUES (?, ?, ?)");
    $stmt->execute([$username, $email, $hashedPassword]);

    echo "User registered successfully!";
}
?>
<form method="POST" action="register.php">
    <input type="text" name="username" placeholder="Username" required>
    <input type="email" name="email" placeholder="Email" required>
    <input type="password" name="password" placeholder="Password" required>
    <button type="submit">Register</button>
</form>

4. User Login Example

Login User (login.php):

<?php
require 'db.php';
session_start();

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $email = $_POST['email'];
    $password = $_POST['password'];

    $stmt = $pdo->prepare("SELECT * FROM users WHERE email = ?");
    $stmt->execute([$email]);
    $user = $stmt->fetch();

    if ($user && password_verify($password, $user['password'])) {
        $_SESSION['user_id'] = $user['id'];
        echo "Login successful!";
    } else {
        echo "Invalid email or password.";
    }
}
?>
<form method="POST" action="login.php">
    <input type="email" name="email" placeholder="Email" required>
    <input type="password" name="password" placeholder="Password" required>
    <button type="submit">Login</button>
</form>

5. Creating and Listing Items

Create Item (create_item.php):

<?php
require 'db.php';
session_start();

if (!isset($_SESSION['user_id'])) {
    die("You must be logged in to list an item.");
}

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $userId = $_SESSION['user_id'];
    $title = $_POST['title'];
    $description = $_POST['description'];
    $price = $_POST['price'];
    $category = $_POST['category'];

    $stmt = $pdo->prepare("INSERT INTO items (user_id, title, description, price, category) VALUES (?, ?, ?, ?, ?)");
    $stmt->execute([$userId, $title, $description, $price, $category]);

    echo "Item listed successfully!";
}
?>
<form method="POST" action="create_item.php">
    <input type="text" name="title" placeholder="Item Title" required>
    <textarea name="description" placeholder="Description" required></textarea>
    <input type="number" step="0.01" name="price" placeholder="Price" required>
    <input type="text" name="category" placeholder="Category" required>
    <button type="submit">List Item</button>
</form>

Display Items (list_items.php):

<?php
require 'db.php';

$stmt = $pdo->query("SELECT items.*, users.username FROM items JOIN users ON items.user_id = users.id");
$items = $stmt->fetchAll();

foreach ($items as $item) {
    echo "<h2>{$item['title']}</h2>";
    echo "<p>{$item['description']}</p>";
    echo "<p>Price: {$item['price']}</p>";
    echo "<p>Category: {$item['category']}</p>";
    echo "<p>Seller: {$item['username']}</p>";
    echo "<hr>";
}

6. Handling Transactions

Purchase Item (purchase_item.php):

<?php
require 'db.php';
session_start();

if (!isset($_SESSION['user_id'])) {
    die("You must be logged in to purchase an item.");
}

if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    $buyerId = $_SESSION['user_id'];
    $itemId = $_POST['item_id'];

    // Fetch item and seller info
    $stmt = $pdo->prepare("SELECT * FROM items WHERE id = ?");
    $stmt->execute([$itemId]);
    $item = $stmt->fetch();

    if ($item) {
        $price = $item['price'];
        $sellerId = $item['user_id'];

        // Begin transaction
        $pdo->beginTransaction();

        // Deduct from buyer's balance
        $stmt = $pdo->prepare("UPDATE users SET balance = balance - ? WHERE id = ?");
        $stmt->execute([$price, $buyerId]);

        // Credit to seller's balance
        $stmt = $pdo->prepare("UPDATE users SET balance = balance + ? WHERE id = ?");
        $stmt->execute([$price, $sellerId]);

        // Record transaction
        $stmt = $pdo->prepare("INSERT INTO transactions (buyer_id, seller_id, item_id, amount) VALUES (?, ?, ?, ?)");
        $stmt->execute([$buyerId, $sellerId, $itemId, $price]);

        // Commit transaction
        $pdo->commit();

        echo "Purchase successful!";
    } else {
        echo "Item not found.";
    }
}
?>
<form method="POST" action="purchase_item.php">
    <input type="hidden" name="item_id" value="ITEM_ID_TO_PURCHASE">
    <button type="submit">Buy Now</button>
</form>

7. Security and Error Handling

Input Validation and Sanitization:
- Always validate and sanitize user inputs using functions like filter_var() and htmlspecialchars().
Error Handling:
- Use try...catch blocks around database operations to handle potential errors gracefully.

8. Additional Features

You can add features such as an admin panel, messaging between users, or a rating system based on your specific needs.

This setup provides a solid foundation for your PHP-based marketplace with MySQL integration.

shopglobal/MUMarket.md