Class in PHP. Creation, properties, methods. Code examples

A class is a code template that is used to create objects. A class is defined using the class keyword followed by an arbitrary class name. The class name can contain any combination of letters and numbers, but must not start with a number. The code associated with the class must be enclosed in curly braces, which are specified after the name. A class definition describes what elements will be contained in each new instance of that class. Based on the data received, let’s see the syntax of the class definition using an example:

class Person{

}

Create an instance

Since a class is a template for creating instances, therefore an object is data that is created and structured according to the template defined in the class.

class Person{

}

$person = new Person();//create class instance

Properties and methods of the class

class Person//create a new class
{ 
    public $name, $age;//let's create new properties of a class, it is essentially usual variables with the public access modifier
      
    function hello() {// method of our class, in essence it is a usual function but in the middle of a class, often with the access modifier
        echo "Hello!<br>";
    }
}
$tom = new Person();//create an instance of the class

$tom->name = "Tom"; // let us turn to our property $name  and set its value "Tom"

$tom->age = 36; 

$personName = $tom->name; //getting the value of the $name property 

$tom->hello(); //call the class method

You can set certain initial values for properties in the class:

class Person
{
	public $name = "Undefined", $age = 18;

	function hello() {
	echo "Hello!<br>";
	}
}

The keyword this is used to refer to the properties (variables) and methods (functions) of the class:

<?php
class Person
{ 
    public $name = "Undefined", $age = 18;
     
    public function displayInfo()
    {
        echo "Name: $this->name; Age: $this->age;//refer to the properties within the class
        
    }
}
$tom = new Person();
$tom -> name = "Tom";
$tom -> displayInfo();   // Name: Tom; Age: 18
?>

Example:

class Person {
    public $name;

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

$person1 = new Person("John");
$person2 = new Person("John");
$person3 = $person1;

var_dump($person1 == $person2);  // Return: bool(true)
var_dump($person1 === $person2); // Return: bool(false)
var_dump($person1 === $person3); // Return: bool(true)

And when using the equivalence operator “===“, both objects are considered equal if both class variables indicate to the same class instance.