How to create classes?

In order to create a class, we group the code that handles a certain topic into one place. For example, we can group all of the code that handles the users of a blog into one class, all of the code that is involved with the publication of the posts in the blog into a second class, and all the code that is devoted to comments into a third class.

To name the class, it is customary to use a singular noun that starts with a capital letter. For example, we can group a code that handles users into a User class, the code that handles posts into a Post class, and the code that is devoted to comments into a Comment class.

For the example given below, we are going to create a Car class into which we will group all of the code which has something to do with cars.

class Car {
  // The code
}

How to add properties to a class?

We call properties to the variables inside a class. Properties can accept values like strings, integers, and booleans (true/false values), like any other variable. Let's add some properties to the Car class.

class Car {
  public $comp;
  public $color = 'beige';
  public $hasSunRoof = true;
}

How to create objects from a class?

We can create several objects from the same class, with each object having its own set of properties.

In order to work with a class, we need to create an object from it. In order to create an object, we use the new keyword. For example:

$bmw = new Car ();

We can create more than one object from the same class.

$bmw = new Car ();
$mercedes = new Car ();

In fact, we can create as many objects as we like from the same class, and then give each object its own set of properties.

How to get an object's properties?

Once we create an object, we can get its properties. For example:

echo $bmw -> color;
echo $mercedes -> color;

How to set the object's properties?

In order to set an object property, we use a similar approach.

For example, in order to set the color to 'blue' in the bmw object:

$bmw -> color = 'blue';

and in order to set the value of the $comp property for both objects:

$bmw -> comp = "BMW";
$mercedes -> comp = "Mercedes Benz";

Once we set the value of a property, we can get its value.

In order to get the color of the $bmw object, we use the following line of code:

echo $bmw -> color;

We can also get the company name and the color of the second car object.

echo $mercedes -> color;
echo $mercedes -> comp;

How to add methods to a class?

The classes most often contain functions. A function inside a class is called a method. Here we add the method hello() to the class with the prefix public.

class Car {
 
  public $comp;
  public $color = 'beige';
  public $hasSunRoof = true;
 
  public function hello() 
  {
    return "beep";
  }
}

We can approach the methods similar to the way that we approach the properties, but we first need to create at least one object from the class.

$bmw = new Car ();
$mercedes = new Car ();
    
echo $bmw -> hello();
echo $mercedes -> hello();

Here is the full code that we have written during this tutorial:

<?php
// Declare the class
class Car {
 
  // properties
  public $comp; 
  public $color = 'beige';
  public $hasSunRoof = true;
 
   // method that says hello
  public function hello()
  {
    return "beep";
  }
}
 
// Create an instance
$bmw = new Car ();
$mercedes = new Car ();
 
// Get the values
echo $bmw -> color; // beige
echo "<br />";
echo $mercedes -> color; // beige
echo "<hr />";
 
// Set the values
$bmw -> color = 'blue';
$bmw -> comp = "BMW";
$mercedes -> comp = "Mercedes Benz";
 
// Get the values again
echo $bmw -> color; // blue
echo "<br />";
echo $mercedes -> color; // beige
echo "<br />";
echo $bmw -> comp; // BMW
echo "<br />";
echo $mercedes -> comp; // Mercedes Benz
echo "<hr />";
 
// Use the methods to get a beep
echo $bmw -> hello(); // beep
echo "<br />";
echo $mercedes -> hello(); // beep