Billing Software

I need a simple billing software made in PHP for a small business.

The software should allow me to add customers, products and prices. I should be able to create a new bill by selecting the customer and adding multiple products with quantity. It should automatically calculate the total amount, tax and final payable amount.

There should be an option to print the bill or save it as PDF.

I also need a page where I can see old bills and search them by customer name, bill number or date.

Admin should be able to add, edit or delete products and customers.

A basic login system is required so only authorized users can use the software.

The design does not need to be very advanced, but it should be simple, clean and easy to use on computer and mobile.

MySQL can be used for the database.