Learn PHP Tutorial

PHP OOP – Constructor


Constructor is a special type of method which automatically initialized upon creation of an object. A class constructor if defined is called whenever a program creates an object of that class.

Constructor method is invoked directly when an object is created from class.

Constructor has a special name in PHP that start with two underscore(__) followed by construct keyword.

Syntax: __construct()

Declaration of Constructors

function __construct()
{
   // initialize the object and its properties by assigning 
   // values
}

The constructors is always defined in the public section of the class. Also, the values to properties of the class are set by Constructors.

Constructor types:

  • Default Constructor – It has no any parameters, but we can pass values to the default constructor dynamically.
  • Parameterized Constructor – It accepts the parameters. We can also pass different values to the data members.
  • Copy Constructor – It accepts the address of the other objects as a parameter.

Let us understand, how constructor work by example –

<?php
class Car{
  public $name;

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

  function get_name() {
    return $this->name;
  }
}

$car= new Car(Volkswagen");
echo $car->get_name();
?>

//OUTPUT
Volkswagen

Another example :

<?php
class Car{
  public $name;
  public $color;

  function __construct($name, $color) {
    $this->name = $name;
    $this->color = $color;
  }
  function get_name() {
    return $this->name;
  }
  function get_color() {
    return "This car color is ". $this->color;
  }
}

$car = new Car("Volkswagen", "red");
echo $car->get_name();
echo "<br>";
echo $car->get_color();
?>

//OUTPUT
Volkswagen
This car color is red