How does Constructor Property Promotion reduce boilerplate in PHP 8+ classes?

Short answer

It lets you declare a property, its type and visibility, and assign it directly in the constructor (__construct) parameters without repeating the code.

Explanation

Previously, creating a property required declaring it above the constructor, accepting it as a constructor parameter, and assigning it with $this->property = $property. In PHP 8, placing public, private, or protected before a constructor parameter tells the engine to create the property and assign its value automatically.

Code example

class User {
    public function __construct(
        public readonly int $id,
        public string $name,
        private string $email
    ) {}
}

Common mistakes

• Using constructor promotion outside the __construct method.

Follow-up questions

• What are Anonymous Classes, and when are they used in PHP?
• What are Readonly Classes in PHP 8.2, and how do they support immutable Value Objects?

Sources

• PHP docs — Constructor Promotion