PHP Tutorial · Object-Oriented PHP · Lesson 30 of 38

PHP Constructors

Initialise objects with __construct and constructor property promotion.

__construct

The constructor runs automatically when you call new. Use it to set up a valid object:

Example 1Try it yourself

<?php
class User
{
    private string $name;
    private array $roles;

    public function __construct(string $name, array $roles = ["member"])
    {
        $this->name = ucfirst($name);
        $this->roles = $roles;
    }

    public function describe(): string
    {
        return $this->name . " (" . implode(", ", $this->roles) . ")";
    }
}

echo (new User("ada"))->describe(), "\n";
echo (new User("lin", ["admin", "editor"]))->describe(), "\n";

Output

Ada (member)
Lin (admin, editor)

Constructor property promotion (PHP 8)

Add a visibility keyword to a constructor parameter and PHP declares and assigns the property for you — far less boilerplate:

Example 2Try it yourself

<?php
class Point
{
    public function __construct(
        public float $x = 0,
        public float $y = 0,
    ) {}

    public function distanceTo(Point $p): float
    {
        return sqrt(($p->x - $this->x) ** 2 + ($p->y - $this->y) ** 2);
    }

    public function __toString(): string
    {
        return "($this->x, $this->y)";
    }
}

$a = new Point(3, 4);
echo "Point $a is ", $a->distanceTo(new Point()), " from the origin\n";

Output

Point (3, 4) is 5 from the origin

Other magic methods

__toString() defines how an object converts to a string; __get, __set and __call intercept access to undefined members (use sparingly).

Test yourself

What is the name of a PHP constructor method?

constructor
__init__
__construct
Class name

Show answer

Answer: __construct