PHP Constructor

Table of Contents

• Introduction
• The __construct() Function

Introduction

We see in the previous section that we can initialize the properties of an object after it has been created by using the -> object operator.

However, a more direct way is to initialize some or all of the properties at the same time we create the object. To do this, we must add a special __construct() function to the class definition. This special method is called the constructor.

The __construct() Function

We continue with the same User class defined in the previous section. In this example, we will be using a constructor function to initialize both properties of an object at the same time it is created.

Example

 1<?php
 2    $object1 = new User('Betty',29); // $object1 created with properties initialized
 3    print_r($object1);
 4
 5    echo "<br>";
 6
 7    $object2 = new User('Julian',32); // $object2 created with properties initialized
 8    print_r($object2);
 9
10    echo "<br>";
11
12
13    echo $object1->get_name(); // calls the get_name() method for $object1
14    echo "<br>";
15    echo $object2->get_age(); // calls the get_age() method for $object2
16
17    class User // Class Definition <<==
18    {
19        public $name, $age; // properties
20
21        function get_name() // method to return $name property
22        {
23            return $this->name;
24        }
25
26        function get_age() // method to return $age property
27        {
28            return $this->age;
29        }
30
31        function __construct($name, $age) // constructor
32        {
33            $this->name = $name;
34            $this->age = $age;
35        }
36    }
37?>

User Object ( [name] => Betty [age] => 29 )
User Object ( [name] => Julian [age] => 32 )
Betty
32

For example, the line echo $object1->get_name() means that we are calling the get_name() method for the object $object1 which prints $this->name or equivalently $object1->name.

This will produce the value of the $name property associated with $object1 which is Betty in this case.