Static Variable Variables

<?php
  class A {
    static function b() {
      echo "It works\n";
    }
  }
  $theClass = "A";
  $x = new $theClass;

  /* Are any of the following legal? Which? */

  A::b();
  $x->b();
  $theClass::b();
?>

Answer: A::b() and $x->b() are legal, $theClass::b() is not.