Title: PHP Price Calculator challenge

Repository: php-pricecalculator-challenge
Type of Challenge: Learning challenge
Duration: 4 days
Deployment strategy : NA
Team challenge : pairs

Learning objectives

Apply basic OOP principles
Import data with a database
Learn to use an MVC

The Mission

Today you are going to combine your new awesome OOP powers with a database. To give you some time to get familiar with a database, this exercise only requires read access, not write access.

Make a price calculator with the following entities:

Customer (Firstname, Lastname)
A customer group (Name)
A product (product name, price in cents)

Notice that the price is in cents stored as an integer, not as a float. This is because you should never store currency as a float. The reason for this is that they store the number with unexpected rounding behavior. For example, it will store 5 as 4.999999999999999999 (scientific fraction), making pennies appear and disappear, once you start to do calculations with multiple floats.

Don't forget to divide by 100 in your PHP code to show the pennies again!

A customer belongs to a customer group, which can also belong to another group (infinite). You don't need to worry for infinite loops in this exercise.

Both a customer and a group can have a discount, which can be a percentage or a fixed amount.

To calculate the price:

For the customer group: In case of variable discounts look for highest discount of all the groups the user has.
If some groups have fixed discounts, count them all up.
Look which discount (fixed or variable) will give the customer the most value.
Now look at the discount of the customer.
First subtract fixed amounts, then percentages!
A price can never be negative.

Importing the data

With this exercise you can find an SQL file you can import into a database, the previous exercise has shown you the command to do this. If done successfully, will create 3 different tables (Customer, Group, Product) with some data inside it.

What is an MVC?

MVC is a classic web design pattern consistent of three levels, and is an extension of the principle of separation of concerns:

The Controller responds to user actions and invokes changes on the model or view as appropriate.
The Model represents the information on which the application operates--its business logic.
The View renders the model into a web page suitable for interaction with the user.

For now you should create 3 different directories:

Controller/: has access to GET/POST vars, receives the Request
Model/: Most of your code should be here, for example the Product and Customer class.
View/: Your HTML files.

While splitting up the Controller & Model is quite intuitive, splitting up the View from the Controller might require a larger change in how you write code. Let us look at some example:

<?php
//oldcode.php
if($_GET['age'] > 18) {
    echo '<h1>You are an adult!</h1>';
} else {
    echo '<h1>You are a child!</h1>';
}

We can split this up into two files:

<?php
//view.php
$sentence = ($_GET['age'] > 18) ? 'You are an adult!' : 'You are a child!';
require 'view.php';

<!-- view.php-->
<h1><?php echo $sentence?></h1>

Must-have features

A dropdown where you can select a Product and a Customer and you get the basic information of the product + the price.
Use a MVC pattern. You can use the MVC Boilerplate.
Use separate objects for importing the entities with SQL, and for managing the entities.

Nice to have features

An actual login page for a customer
A table where you can see in detail how the price is calculated
The possibility to have different prices for different quantities (look, 1 EUR per item for 1, 0.9 EUR per item for 100, ...)
A category page for the different products

Discussion for friday

Do you prefer procedural code or object oriented one? Why?
What is the use of an MVC? Do you prefer another way of structuring your code? SAVE TO CACHER

Hassanalihazaraa/Price-calculator