<?php
  class the_class {
    public $var = 'foo';
  }
  class my_other_class {
    public function __construct(the_class $obj) {
      echo $obj->var;
    }
  }
  $a = new the_class;
  $b = new my_other_class($a);
  $c = new my_other_class($b);
?>