How can PHP developers ensure proper normalization of data when designing database tables for a PHP application, such as in the case of storing invoice data?

To ensure proper normalization of data when designing database tables for a PHP application, PHP developers should follow the principles of database normalization, such as breaking down data into smaller, related tables to reduce redundancy and improve data integrity. In the case of storing invoice data, this could involve creating separate tables for customers, products, invoices, and invoice items, and establishing relationships between them using foreign keys.

CREATE TABLE customers (
    id INT PRIMARY KEY,
    name VARCHAR(255),
    email VARCHAR(255)
);

CREATE TABLE products (
    id INT PRIMARY KEY,
    name VARCHAR(255),
    price DECIMAL(10, 2)
);

CREATE TABLE invoices (
    id INT PRIMARY KEY,
    customer_id INT,
    date DATE,
    total_amount DECIMAL(10, 2),
    FOREIGN KEY (customer_id) REFERENCES customers(id)
);

CREATE TABLE invoice_items (
    id INT PRIMARY KEY,
    invoice_id INT,
    product_id INT,
    quantity INT,
    subtotal DECIMAL(10, 2),
    FOREIGN KEY (invoice_id) REFERENCES invoices(id),
    FOREIGN KEY (product_id) REFERENCES products(id)
);