OOP Training project

How to run the project

Configuration

cp config/database.local.php.dist config/database.local.php

Then edit config/database.local.php and set your own variables, or remove the key to enable the global configuration.

Serveur PHP

Either you can use a local server or the PHP integrated development server.

Using the latter, run the following command (given your port 8888 is free):

php -S localhost:8888

Then visit http://localhost:8888.

Database

You'll need a mysql 5.7 database to run the project. Data are located in resources/env/local/fixtures.

Glossary

• attribute: variable located inside a class that stores a part of the state of that class. It is sometimes used in place of the property (see definition), but while the property is a collaborator, the attribute is a part of the definition of the class.
• collaborator: object that interacts with another object in order to produce a given result.
• autoloading: in an interpreted language where there is no compilation nor assembly, classes are not referenced in a single location, hence the need for a method allowing the retrieval of the definition of the class. The autoloading is therefore the mechanism used to retrieve said classes.
• behaviour/behavior: description of a characteristic or an intention of an object. Formalised with interface in most languages.
• class: structure made of attributes, properties and methods.
• method: function contained in a class, implementation of behaviour.
• encapsulation: ability for an object not to disclose its actual state nor the actual underlying implementation of the characteristics on which the behaviour exposed is based.
• entity: object with a lifetime, which evolves and represents an element of the business/the domain. It has a unique identifier, and equality is defined by comparing this identifier.
• instance: variable resulting from the creation of an object of a given class.
• member variable: attribute or property
• method: function in a class.
• namespace: an abstract container or environment created to hold a logical grouping of unique identifiers or symbols (i.e. names). Very useful for using short contextualised names and to explicit naming.
• new keyword: keyword to allow the creation of a new instance of a class.
• object: instance of class.
• property: member variable that refers to a third party attribute, act as a owning side of a relation.
• value object: object for which the sole purpose it to store a value after having validated it, and then expose it back.
• visibility (private, protected, public): defines who can access a structure's content.
• state: current value of an element.
• PSR:
• PHP-FIG
• static
• scope
• this
• immutability
• interface
• inheritance
• composition
• abstraction
• overriding
• overloading
• method signature
• code style
• Generics
• Typed collection
• Repository
• MVC/ADR
• polymorphism
• constructor
• dependency injection
• dependency inversion
• dependency injection container
• relations
• aggregation

Exemple

A Character has a force and a sword, and is able to fight.

The class is Character, the force is an attribute, the sword is a property and fight is a method.

Considering $character1 = new Character(), $character1 is a variable containing an instance of the class Character. The value of the variable $character1 is therefore an object.

Adding $character2 = new Character(), the value of the variable $character2 is another instance of the class Character.

Syntax basics

In OOP (except for languages like es5 and older javascript), one can define structures that are able to store data as well as expose a behaviour. These structures are named classes.

class User
{

}

In a class, the values stored (state) are named member variable, properties or attributes (even though these terms are not mathematically equal, they are equivalent as the nuance introduced is minimal).

class User
{
    var $property;
    var $memberVariable;
    var $attribute;
}

On top of the state, the class contains the definition of behaviour, using the form of a function, for which the scope is limited to the class. These are named method.

class User
{
    var $property;
    var $memberVariable;
    var $attribute;
    
    function thisIsABehaviour()
    {
    }
}

Now that the structure is defined, one (as in "the developer") can use it in one's code. The variable containing an instance of a class is named an object.

$myUser = new User();

Notice the new keyword above, meaning variable will contain an instance of the class.

Step 1: project definition

The project consists at first in creating a web application that only lists invoices.

An invoice is made of total price tax included, a creation date, a customer name and a customer address.

The latter requirement let us consider having different objects