Challenge 3 — Solution

Task: Create a trait Greetable with a method sayHello() that echoes
"Hello from " followed by a $name property. Use this trait in two
unrelated classes, Robot and Alien (neither extending the other, or any
common parent), each with their own $name set via a constructor. Call
sayHello() on one instance of each.

<?php
    trait Greetable {
        public function sayHello() {
            echo "Hello from {$this->name}<br>";
        }
    }

    class Robot {
        use Greetable;

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

    class Alien {
        use Greetable;

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

    $robot = new Robot("Unit-7");
    $alien = new Alien("Zorblax");

    $robot->sayHello();
    $alien->sayHello();
?>


Output:
Hello from Unit-7
Hello from Zorblax

Notes:
- Robot and Alien share no inheritance relationship whatsoever - one
  does not extend the other, and neither extends any common parent
  class - yet both gain the identical sayHello() method purely by
  writing "use Greetable;" inside their own class body.
- The trait's own sayHello() method references $this->name, which
  works correctly for both classes because each one independently
  declares its own $name property via its own constructor - the trait
  itself declares no properties, it only supplies the method code.
- This is exactly the scenario extends cannot solve cleanly: sharing
  actual, identical method code across classes that have no genuine
  "is-a" relationship to each other.