What are some best practices for handling database normalization and data relationships in PHP scripts?

Database normalization is the process of organizing data in a database efficiently by reducing redundancy and dependency. When working with data relationships in PHP scripts, it is important to follow normalization principles to ensure data integrity and optimize performance. One best practice for handling database normalization and data relationships in PHP scripts is to use foreign keys to establish relationships between tables. This helps maintain referential integrity and ensures that data is consistent across related tables.

```php
CREATE TABLE users (
    id INT PRIMARY KEY,
    name VARCHAR(50)
);

CREATE TABLE orders (
    id INT PRIMARY KEY,
    user_id INT,
    order_date DATE,
    FOREIGN KEY (user_id) REFERENCES users(id)
);
```

In this example, the `orders` table has a foreign key `user_id` that references the `id` column in the `users` table, establishing a relationship between the two tables. This ensures that every order is associated with a valid user in the database.