Abstraction, Encapsulation, Polymorphism, and Interfaces: whether you’ve been programming in PHP for years or are just starting your journey, these terms can be overwhelming even on a good day. Variables, conditionals, those all make sense. But this whole Object-Oriented thing is WAY more complicated. Not only that, people that already understand it act like it’s so easy and they talk right over the simple questions and never explain the basic concepts in a way that actually makes sense. In this session we’ll take you through real life examples of Object-Oriented terminology in a way that will make sense of all the mumbo jumbo and allow you to utilizing OOP immediately.

1. Demystifying
Object-Oriented Programming
.

2. Presented by: Alena Holligan
• Wife, and Mother of 3 young children
• PHP Teacher at Treehouse
• Portland PHP User Group Leader
www.sketchings.com
@sketchings
alena@holligan.us

3. PART 1: Terminology
Class (properties, methods, this)
Object
Instance
Abstraction
Encapsulation

4. PART 2: Polymorphism
Inheritance
Interface
Abstract Class
Traits

5. PART 3: Magic
Magic Methods
Magic Constants
Static Properties and Methods

6. PART 1: Terminology

7. Class
A template/blueprint that facilitates creation of
objects. A set of program statements to do a certain
task. Usually represents a noun, such as a person,
place or thing.
Includes properties and methods — which are class
functions

8. Object
Instance of a class.
In the real world object is a material thing that can be
seen and touched.
In OOP, object is a self-contained entity that consists
of both data and procedures.

9. Instance
Single occurrence/copy of an object
There might be one or several objects, but an
instance is a specific copy, to which you can have a
reference

10. class User { //class
public $name; //property
public function getName() { //method
echo $this->name; //current object property
}
}
$user1 = new User(); //first instance of object
$user2 = new User(); //second instance of object

11. Abstraction
Managing the complexity of the system
Dealing with ideas rather than events
This is the class architecture itself.
Use something without knowing inner workings

12. Encapsulation
Binds together the data
and functions that
manipulate the data, and
keeps both safe from
outside interference and
misuse.
Properties
Methods

13. Team-up
OOP is great for working in groups

14. Team Challenges
Write a class with properties and methods
Example: User class with name, title, and salutation

15. PART 2:
Polymorphism
D-R-Y
Sharing Code

16. pol·y·mor·phism
/ˌpälēˈmôrfizəm/
The condition of occurring in several different forms
BIOLOGY
GENETICS
BIOCHEMISTRY
COMPUTING

17. Terms
Polymorphism
Inheritance
Interface
Abstract Class
Traits

18. Inheritance: passes knowledge down
Subclass, parent and a child relationship, allows for
reusability, extensibility.
Additional code to an existing class without modifying it.
Uses keyword “extends”
NUTSHELL: create a new class based on an existing class
with more data, create new objects based on this class

19. Creating a child class
class Developer extends User {
public $skills = array(); //additional property
public function getSkillsString(){ //additional method
return implode(", ",$this->skills);
}
public function getSalutation() {//override method
return $this->title . " " . $this->name. ", Developer";
}
}

20. Using a child class
$developer = new Developer();
$developer->setName(”Jane Smith”);
$developer->setTitle(“Ms”);
echo $developer->getFormatedSalutation();
$developer->skills = array("JavasScript", "HTML", "CSS");
$developer->skills[] = “PHP";
echo $developer->getSkillsString();
When the script is run, it will return:
Ms Jane Smith, Developer
JavasScript, HTML, CSS, PHP

21. Team Challenges
Extend the User class for another type of user, such as our
Developer example

22. Interface
Interface, specifies which methods a class must implement.
All methods in interface must be public.
Multiple interfaces can be implemented by using comma
separation
Interface may contain a CONSTANT, but may not be
overridden by implementing class

23. interface UserInterface {
public function getFormattedSalutation();
public function getName();
public function setName($name);
public function getTitle();
public function setTitle($title);
}
class User implements UserInterface { … }

24. Team Challenges
Add an Interface for your Class

25. Abstract Class
An abstract class is a mix between an interface and a
class. It can define functionality as well as interface.
Classes extending an abstract class must implement all
of the abstract methods defined in the abstract class.

26. abstract class User { //abstract class
public $name; //class property
public getName() { //class method
echo $this->name;
}
abstract public function setName($name); //abstract method
}
class Developer extends User {
public setName($name) { //implementing the method
…

27. Team Challenges
Change to User class to an abstract class.
Try instantiating the User class

28. Traits
Composition
Horizontal Code Reuse
Multiple traits can be implemented

29. Creating Traits
trait Toolkit {
public $tools = array();
public function setTools($task) {
switch ($task) {
case “eat":
$this->tools =
array("Spoon", "Fork", "Knife");
break;
...
}
}
public function showTools() {
return implode(", ",$this->skills);
}
}

30. Using Traits
class Developer extends User {
use Toolkit;
...
}
$developer = new Developer();
$developer->setTools("Eat");
echo $developer->showTools();
When run the script returns:
Spoon, Fork, Knife

31. When run, the script returns:
Ms Jane Smith
Spoon, Fork, Knife

32. Team Challenges
Add a trait to the User

33. PART 3: Magic
Magic Methods
Magic Constants
Static Properties and Methods

34. Magic Methods
Setup just like any other method
The Magic comes from the fact that they are
triggered and not called
For more see http://php.net/manual/en/
language.oop5.magic.php

35. Magic Constants
Predefined functions in PHP
For more see http://php.net/manual/en/
language.constants.predefined.php

36. Using Magic Methods and Constants
class User {
...
public function __construct($name, $title) {
$this->name = $name;
$this->title = $title;
}
public function __toString() {
return __CLASS__. “: “
. $this->getFormattedSalutation();
}
...
}

37. Creating / Using the Magic Method
$user = new User("Jane Smith","Ms");
echo $user;
When the script is run, it will return:
User: Ms Jane Smith

38. Challenges
Add a Magic Method
Add a Magic Constants

39. Static Properties and Methods
class User {
public static $encouragements = array(
“You are beautiful!”,
“You have this!”,
public static function encourage()
{
$int = rand(count($this->encouragements));
return self::encouragements[$int];
}
...
}

40. Using the Static Method
echo User::encourage();
When the script is run, it will return:
You have this!

41. Team Challenge
Add and use a Static Method

42. The FINAL Keyword
Prevents child classes from overriding a method by
prefixing the definition with final.
If the class itself is being defined final then it cannot
be extended.

43. class User { //can extend
final public getName() { //cannot extend
echo $this->name;
}
final class Developer extends User { //cannot extend
public getName() { //error
echo “My Name is: ” .$this->name;
}
class Manager extends Developer {…} //error

44. Team Challenges
Define a parent method as FINAL and try to override in the child
Define a class as FINAL and try to create a child

45. Resources
LeanPub: The Essentials of Object Oriented PHP
Head First Object-Oriented Analysis and Design

46. Presented by: Alena Holligan
• Wife and Mother of 3 young children
• PHP Teacher at Treehouse
• Portland PHP User Group Leader
www.sketchings.com
@sketchings
alena@holligan.us
Download Files: https://github.com/sketchings/oop-basics
https://joind.in/talk/131c4