OOP in PHP

Welcome to ‘Intro to OOP with PHP’ part 1
Thank you for your interest. Files can be found
at https://github.com/sketchings/oop-basics
Contact Info:
www.sketchings.com
@sketchings
alena@holligan.us

Intro to OOP with PHP
a basic look into object-oriented programming

Basic PHP to make sure your running
<html>
<body>
<?php echo “Hello world!”; ?>
</body>
</html>

What is OOP?
➔ Object-Oriented Programing
➔ A programming concept that treats
functions and data as objects.
➔ A programming methodology based on
objects, instead of functions and
procedures

OOP vs Procedural or Functional
OOP is built around the "nouns", the things in
the system, and what they are capable of
Whereas procedural or functional
programming is built around the "verbs" of the
system, the things you want the system to do

Terminology
the single most important part

Terms
Class (properties, methods)
Object
Instance
Abstraction
Encapsulation
Inheritance

Terms continued
Polymorphism
Interface
Abstract
Type Hinting
vs Type Casting
Namespaces

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

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.

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

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

Abstraction
“An abstraction denotes the essential
characteristics of an object that distinguish it
from all other kinds of object and thus provide
crisply defined conceptual boundaries,
relative to the perspective of the viewer.”
— G. Booch
This is the class architecture itself.

Encapsulation
Scope. Controls who can access what.
Restricting access to some of the object’s
components (properties and methods),
preventing unauthorized access.
● Public - everyone
● Protected - inherited classes
● Private - class itself, not children

class User {
protected $name;
protected $title;
public function getFormattedSalutation() {
return $this->getSalutation();
}
protected function getSalutation() {
return $this->title . " " . $this->name;
}
public function getName() {
return $this->name;
}
public function setName($name) {
$this->name = $name;
}
public function getTitle() {
return $this->title;
}
public function setTitle($title) {
$this->title = $title;
}
}

$user = new User();
$user->setName("Jane Smith");
$user->setTitle("Ms");
echo $user->getFormattedSalutation();
When the script is run, it will return:
Ms Jane Smith
Creating / Using the object Instance

class User {
protected $name;
protected $title;
public function __construct($name, $title) {
$this->name = $name;
$this->title = $title;
}
public function __toString() {
return $this->getFormattedSalutation();
}
...
}
For more see http://php.net/manual/en/language.oop5.magic.php
Constructor Method & Magic Methods

$user = new User("Jane Smith","Ms");
echo $user;
When the script is run, it will return:
Ms Jane Smith
the same result as before
Creating / Using the object Instance

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

class Developer extends User {
public $skills = array();
public function getSalutation() {
return $this->title . " " . $this->name. ", Developer";
}
public function getSkillsString() {
echo implode(", ",$this->skills);
}
}
$developer = new Developer("Jane Smith", "Ms");
echo $developer;
echo "<br />";
$developer->skills = array("JavasScript", "HTML", "CSS");
$developer->skills[] = "PHP";
$developer->getSkillsString();
Creating and using a child class

When run, the script returns:
Ms Jane Smith
JavasScript, HTML, CSS, PHP

Polymorphism
Polymorphism describes a pattern in object
oriented programming in which classes have
different functionality while sharing a common
interface

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

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

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

abstract class User { //class
public $name; //property
echo $this->name;
}
abstract public function setName($name);
}
class Developer extends User { … }

Type Hinting
Functions are now able to force parameters to
be objects, interfaces, arrays or callable.
However, if NULL is used as the default
parameter value, it will be allowed as an
argument for any later call.
If class or interface is specified as type hint,
all its children/implementations are allowed.

class Resume {
public $user;
public function __construct(User $user) {
$this->user = $user;
}
public function formatHTML() {
$string = $this->user->getName();
...
}
}
$resume = new Resume($developer);

Namespaces
- Help create a new layer of code encapsulation
- Keep properties from colliding between areas of
your code
- Only classes, interfaces, functions and constants
are affected
- Anything that does not have a namespace is
considered in the Global namespace (namespace = "")

Namespaces
- must be declared first (except 'declare)
- Can define multiple in the same file
- You can define that something be used in the
"Global" namespace by enclosing a non-labeled
namespace in {} brackets.
- Use namespaces from within other
namespaces, along with aliasing

namespace myUser;
class User { //class
public $name; //property
echo $this->name;
}
public function setName($name);
}
class Developer extends myUserUser { … }

Explanation Complete
Question and Answer Time

Where to go from here
Resources and other things to look into

Strengthen your skills
Code Review
Pair/peer programing
Contribute to open source
Open up a personal project
Continuous learning
Participate in the community, meetups,
conferences, forums, teach

Online Training
NomadPHP.com
TeamTreehouse.com (locally on meetup)
learnhowtoprogram.com (by epicodus)
codeschool.com (great GIT intro)
freecodecamp.com, coursera.org, udemy.
com, lynda.com

Books
Design Patterns: Elements of Reusable Object-Oriented
Software - by Erich Gamma
Mastering Object Oriented PHP - by Brandon Savage
Python 3 Object Oriented Programming - by Dusty Phillips
Practical Object-Oriented Design in Ruby - by Sandi Metz
Clean Code / The Clean Coder - both by Robert Martin
The Pragmatic Programmer – by Andrew Hunt/David Thomas
Refactoring: Improving the Design of Existing Code
- by Martin Fowler

Podcasts, Videos and People
Listing: phppodcasts.com
Voices of the Elephpant
PHP Roundtable
YouTube: PHPUserGroup
NomadPHP
People: @CalEvans, @LornaJane, @adamculp
https://twitter.com/sketchings/lists/php

Challenges
1. Change to User class to an abstract class.
2. Throw an error because your access is too
restricted.
3. Extend the User class for another type of
user, such as our Developer example
4. Define 2 “User” classes in one file using
namespacing

Finished
Question and Answer Time

Thank You from Alena Holligan
Help me improve:
Survey: http://goo.gl/forms/4Huh9uCSGD
Joind.in: https://joind.in/event/php-oop1
Contact Info:
www.sketchings.com
@sketchings
alena@holligan.us

OOP in PHP

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