Solution Review: Static Methods & Properties and Traits

<?php 
interface User {}
trait Writing {
  abstract public function writeContent();
}
class Author implements User { 
  use Writing;
  public function writeContent() {
    return "Author, please start typing an article"; 
  }
}
class Commentator implements User { 
  use Writing;
  public function writeContent() {
    return "Commentator, please start typing your comment"; 
  }
}
class Viewer implements User {}
function test()
{
  $author1 = new Author();
  $commentator1 = new Commentator();
  return $author1 -> writeContent() . " and " . $commentator1 -> writeContent();
}
echo test()
?>