Classes and Objects

Classes group state and behavior. Keep properties private or readonly where possible and expose operations that preserve valid state.

Practical example

<?php
final class Percentage {
  public function __construct(public readonly float $value) {
    if ($value < 0 || $value > 100) throw new InvalidArgumentException('0..100 required');
  }
  public function asRatio(): float { return $this->value / 100; }
}

$this is the receiver. Static mutable state hides dependencies and complicates long-running workers. Magic methods should remain unsurprising. Prefer small cohesive objects, explicit collaborators, and value objects for stable domain concepts.