PHP Class Example: Build a User Class Step by Step

Let us build a small User class that uses what you learned in this chapter: a constructor, typed properties, private data, validation, methods and __toString().

Step 1: the data

index.php

PHP

<?php
class User
{
    public function __construct(
        private string $name,
        private string $email,
    ) {}

    public function name(): string
    {
        return $this->name;
    }
}

$user = new User("Isha", "isha@example.com");

echo $user->name();

Output

OUTPUT

Isha

Step 2: validate in the constructor

A User should never exist with an invalid email.

index.php

PHP

<?php
class User
{
    public function __construct(
        private string $name,
        private string $email,
    ) {
        $this->name = trim($name);

        if ($this->name === "") {
            throw new InvalidArgumentException("Name is required.");
        }

        if (filter_var($email, FILTER_VALIDATE_EMAIL) === false) {
            throw new InvalidArgumentException("Invalid email: $email");
        }
    }
}

try {
    new User("  ", "isha@example.com");
} catch (InvalidArgumentException $e) {
    echo $e->getMessage();
}

Output

OUTPUT

Name is required.

Step 3: behaviour

index.php

PHP

<?php
class User
{
    private bool $active = true;

    public function __construct(
        private string $name,
        private string $email,
    ) {}

    public function name(): string
    {
        return $this->name;
    }

    public function email(): string
    {
        return $this->email;
    }

    public function deactivate(): void
    {
        $this->active = false;
    }

    public function isActive(): bool
    {
        return $this->active;
    }

    public function initials(): string
    {
        $parts = explode(" ", $this->name);

        return strtoupper(implode("", array_map(fn($p) => $p[0], $parts)));
    }

    public function __toString(): string
    {
        return $this->name . " <" . $this->email . ">";
    }
}

$user = new User("Isha Rao", "isha@example.com");

echo $user . "\n";
echo $user->initials() . "\n";
$user->deactivate();
var_dump($user->isActive());

Output

OUTPUT

1
2
3

Isha Rao <isha@example.com>
IR
bool(false)

What you used

A constructor with promoted, typed, private properties.
Validation that keeps the object always valid.
Private data with public methods as the only way in.
__toString() to print the object.

Exercise 1: a Product class

Create a Product with a name and a price (both required). The price must be positive. Add a method priceWithTax(float $rate = 18): float and a __toString() that returns something like Pen: 12.00.

Show a possible solution

index.php

PHP

<?php
class Product
{
    public function __construct(
        private string $name,
        private float $price,
    ) {
        if ($price <= 0) {
            throw new InvalidArgumentException("Price must be positive.");
        }
    }

    public function priceWithTax(float $rate = 18): float
    {
        return round($this->price * (1 + $rate / 100), 2);
    }

    public function __toString(): string
    {
        return $this->name . ": " . number_format($this->price, 2);
    }
}

$p = new Product("Pen", 12);

echo $p . "\n";
echo $p->priceWithTax();

Output

OUTPUT

1
2

Pen: 12.00
14.16

Exercise 2: a shopping cart class

Create a Cart class with add(string $item, float $price), total(): float and count(): int. Keep the items private.

Show a possible solution

index.php

PHP

<?php
class Cart
{
    private array $items = [];

    public function add(string $item, float $price): static
    {
        $this->items[] = ["item" => $item, "price" => $price];
        return $this;
    }

    public function total(): float
    {
        return array_sum(array_column($this->items, "price"));
    }

    public function count(): int
    {
        return count($this->items);
    }
}

$cart = (new Cart())->add("Pen", 12)->add("Book", 250);

echo $cart->count() . " items, total " . $cart->total();

Output

OUTPUT

2 items, total 262