PHP Constructor

A constructor in PHP is a special type of function that is automatically called when an object of a class is created. Constructors are typically used to initialize properties of a class when an object is instantiated.

Here's a simple example to illustrate the concept of constructors in PHP:

Example 1: Basic Constructor

<?php
class Car {
    public $make;
    public $model;

    // Constructor
    public function __construct($make, $model) {
        $this->make = $make;
        $this->model = $model;
    }

    public function getDetails() {
        return "Make: " . $this->make . ", Model: " . $this->model;
    }
}

// Create an object of Car
$car1 = new Car("Toyota", "Corolla");
echo $car1->getDetails(); // Output: Make: Toyota, Model: Corolla
?>

In this example, the Car class has a constructor method __construct that takes two parameters: $make and $model. When a Car object is created, the constructor is called with the specified arguments, and the properties $make and $model are initialized.

Example 2: Constructor with Default Values

You can also define default values for the constructor parameters:

<?php
class Car {
    public $make;
    public $model;

    // Constructor with default values
    public function __construct($make = "Unknown", $model = "Unknown") {
        $this->make = $make;
        $this->model = $model;
    }

    public function getDetails() {
        return "Make: " . $this->make . ", Model: " . $this->model;
    }
}

// Create an object of Car without arguments
$car2 = new Car();
echo $car2->getDetails(); // Output: Make: Unknown, Model: Unknown

// Create an object of Car with arguments
$car3 = new Car("Honda", "Civic");
echo $car3->getDetails(); // Output: Make: Honda, Model: Civic
?>

In this example, if no arguments are provided when creating a Car object, the constructor will use the default values "Unknown" for both $make and $model.

Example 3: Using Constructors with Inheritance

When dealing with inheritance, the child class can call the parent class constructor using parent::__construct().

<?php
class Vehicle {
    public $make;

    // Parent constructor
    public function __construct($make) {
        $this->make = $make;
    }
}

class Car extends Vehicle {
    public $model;

    // Child constructor
    public function __construct($make, $model) {
        parent::__construct($make); // Call the parent constructor
        $this->model = $model;
    }

    public function getDetails() {
        return "Make: " . $this->make . ", Model: " . $this->model;
    }
}

// Create an object of Car
$car4 = new Car("Ford", "Focus");
echo $car4->getDetails(); // Output: Make: Ford, Model: Focus
?>

In this example, the Car class inherits from the Vehicle class. The constructor of the Car class calls the constructor of the Vehicle class using parent::__construct($make) to initialize the make property.

These examples show how constructors are used in PHP to initialize objects and manage inheritance.