Challenge 2 — Solution

Task: Create an abstract class Employee with a constructor setting
$name, an abstract method calculatePay(): float, and a concrete method
describe() that echoes the name and calculated pay together. Create two
subclasses, SalariedEmployee and HourlyEmployee, each implementing
calculatePay() differently.

<?php
    abstract class Employee {
        public function __construct(protected string $name) {}

        abstract public function calculatePay(): float;

        public function describe() {
            echo "{$this->name}: £" . number_format($this->calculatePay(), 2) . "<br>";
        }
    }

    class SalariedEmployee extends Employee {
        public function __construct(string $name, private float $annualSalary) {
            parent::__construct($name);
        }

        public function calculatePay(): float {
            return $this->annualSalary / 12;
        }
    }

    class HourlyEmployee extends Employee {
        public function __construct(string $name, private float $hourlyRate, private float $hoursWorked) {
            parent::__construct($name);
        }

        public function calculatePay(): float {
            return $this->hourlyRate * $this->hoursWorked;
        }
    }

    $salaried = new SalariedEmployee("Priya", 48000);
    $hourly = new HourlyEmployee("Tom", 15.50, 37);

    $salaried->describe();
    $hourly->describe();
?>


Output:
Priya: £4,000.00
Tom: £573.50

Notes:
- Employee cannot be instantiated directly with "new Employee(...)" -
  it exists purely to be extended, and its abstract calculatePay()
  method guarantees every subclass must provide its own implementation.
- describe() is written once, on the abstract parent, and works
  correctly for both subclasses without any changes - it calls
  $this->calculatePay(), which resolves to whichever subclass's own
  version is appropriate for the object it's called on.
- Each subclass's own constructor calls parent::__construct($name) to
  reuse Employee's own name-setting logic, then adds its own additional
  properties ($annualSalary or $hourlyRate/$hoursWorked) specific to
  that particular kind of employee.