PHP for beginners - Part 7 - Classes?...Like school?

Part 7

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Chapter 12 - Classes 101

Chapter 12 - Classes 101

What is a class? Well, according to Wikipedia, this is what a programming class is:
In object-oriented programming, a class is an extensible program-code-template for creating objects, providing initial values for state (member variables) and implementations of behavior (member functions or methods)

What does that mean? A class is very simply a way of packaging variables and functions within a template to be reused or extended.

Yea but what does that mean? Its kind of hard to wrap your head around, but lets dive into what classes do in PHP and how to make them. This will better help you understand what’s going on.

Syntax

Php 
class Task {

}

Wow thats it? Yes, technically this is all a class needs, however this isnt very dynamic, so lets extend it a little.

Php 
class Task {
  protected $description;

  public function __construct($description) {
    $this->$description;
  }
}

This is a very basic example and intro to classes. Lets break it down now.

class Task Define the class name
protected $description; initialize the variable $description
public function __construct($description) This is a special ‘constructor’ function.
This means that when a class is ‘instantiated’, to run the following code. Or in other words when you create a ‘new’ class, do the run the following code.
$this->$description; ahhhh yes. The magical ‘$this’. In some languages it may just be this or self. This is a tough term to wrap your head around so let’s keep it simple.

In this case $this means, for THIS instance of Task, set the value provided in the constructor to this instance’s $description variable

So what the heck does that above statment even mean? Well let’s continue on. Examples explain this better than I can. Lets instantiate a the class Task now.

Php 
$task = new Task('I am a description');
var_dump($task);

This will very simply provide a nice human readable version of task displayed in the web browser of your choice.

Okay, this is great and all, but we can’t do anything with this right now.

You could try

Php 
$task = new Task('I am a description');
var_dump($task->$description);

But you’ll get an access error. So let’s talk about getters and setters. A getter simply ‘gets’ a value from a class and a setter ‘sets’ a value in a class. Getters and setters are part of a OOP term called ‘encapsulation’. Don’t worry about what that means for now, just know that it may come up in the future. Not very useful, but lets see how it works.

Php 
class Task {
  protected $description;

  public function __construct($description){
    $this->$description;
  }

  public function getDescription(){
    return $this->description;
  }

  public function setDescription($description){
    $this->description = $description;
  }
}

$task = new Task("Go to the store");


The above defines the class Task. Now lets see how we would access values.

Php 
// ...above code omitted for brevity

// Accessing the value of $task->description
var_dump($task->getDescription();

// Changes the value of $task->description to the new description
$task->setDescription("Go to grandma's house");
var_dump($task->getDescription();
// Will now var_dump "Go to grandma's house" instead of "go to store"


Now what if we want to make multiple tasks and store them in an array? Simple:

Php 
// ...above code omitted for brevity
$tasks = [
  new Task("Go to store"),
  new Task("Go to grandma's house"),
  new Task("Go home")
];

var_dump($tasks);

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