Building an e-book store with PHP involves several steps. Here is a step-by-step guide on how to build an e-book store using PHP:

1. Set up the database: Create a database to store information about e-books, such as title, author, price, description, and cover image. You can use a tool like phpMyAdmin or the command line to create the database. Create a table to store the e-book data.

2. Create PHP classes: Create PHP classes to interact with the database and perform operations such as adding, updating, and deleting e-books. You can create classes like Ebook, EbookManager, and DatabaseManager.

3. Design the front-end: Create HTML templates to display e-books on the front-end. You can use CSS to style the templates and make them visually appealing. Use PHP code to fetch e-book data from the database and populate the templates dynamically.

4. Implement the CRUD operations: Use PHP to implement the CRUD (Create, Read, Update, Delete) operations for e-books. Write PHP functions to add new e-books, retrieve e-books from the database, update e-books, and delete e-books. These functions should interact with the database through the database class.

5. Add search functionality: Implement search functionality to allow users to search for e-books based on title, author, or other criteria. Create a search form that sends the search query to the server, and write PHP code to retrieve matching e-books from the database.

6. Implement user authentication: If you want to allow users to create accounts and make purchases, implement user authentication functionality. Create a user table in the database to store user information like username, password, and email. Use PHP to handle user registration, login, and logout.

7. Implement shopping cart functionality: If you want to allow users to add e-books to a shopping cart and make purchases, implement shopping cart functionality. Create a table in the database to store shopping cart items. Use PHP to handle adding items to the cart, updating quantities, and checking out.

8. Implement payment integration: If you want to handle payments for e-book purchases, integrate with a payment gateway like PayPal or Stripe. Use their API documentation to implement the necessary PHP code to handle payments.

9. Implement user reviews and ratings: Allow users to review and rate e-books. Create a table in the database to store user reviews and implement the necessary PHP code to display reviews and ratings on the e-book detail page.

10. Test and deploy: Test your e-book store thoroughly to ensure all functionality is working as expected. Deploy your e-book store to a hosting provider or a server so that it can be accessed by users.

Remember to follow best practices for security, such as validating and sanitizing user input, protecting against SQL injection attacks, and using secure HTTPS connections for sensitive data.