MyHelloWorld::setWorld PHP Method

    public function setWorld($val)
    {
        $this->world = $val;
    }

Express requirements of a trait by abstract methods.
--FILE--
<?php 
error_reporting(E_ALL);
trait Hello
{
    public function sayHelloWorld()
    {
        echo 'Hello' . $this->getWorld();
    }
    public abstract function getWorld();
}
class MyHelloWorld
{
    private $world;
    use Hello;
    public function getWorld()
    {
        return $this->world;
    }
    public function setWorld($val)
    {
        $this->world = $val;
    }
}
$o = new MyHelloWorld();
$o->setWorld(' World!');
$o->sayHelloWorld();
?>
--EXPECTF--
Hello World!