通过引用修改数组的问题

Question

In PHP, I have the following code (whittled down, to make it easier to read):

class Var {
  public $arr;
  function __construct($arr) {
    $this->arr = $arr;
  }
  function set($k, $v) {
    $this->arr[$k] = $v;
  }
}

class Session extends Var {
  function __construct() {}
  function init() {
    session_start();
    parent::__construct($_SESSION);
  }
}

$s = new Session();
$s->init();
$s->set('foo', 'bar');

var_dump($_SESSION);

At this point, I want $_SESSION to contain 'foo' => 'bar'. However, the $_SESSION variable is completely empty. Why is this the case? How can I store the $_SESSION variable as a property in order to later modify it by reference?

I have tried replacing __construct($arr) with __construct(&$arr), but that did not work.

Answer 1

You needed to take care of reference on every variable re-assignment you have.

So the first place is __construct(&$arr)

The second is $this->arr = &$arr;

Then it should work.

If you didn't put the & in the latter case - it would "make a copy" for the reference you passed in constructor and assign "a copy" to the $this->arr.

PS: It's really weird to call parent constructor from non-constructor method