Re: references, circular references, oop, and garbage collection in PHP5

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[ man.. I just realized that "reply" to this list doesn't send to the list... replies being re-sent... thanks for the help! ]

On Dec 6, 2005, at 10:45 PM, Curt Zirzow wrote:

I'm going to jump to the code as fast as possible to explain what I
can, the key thing to remember in php5 is that the old &$var
declaration has no real meaning in objects.  php5's objects exist
outside of the old oop reference. Consider:

class Object {
  public $val;
  function __construct($v) {
    $this->val = $v;
  }
}

In PHP5:

  $o = new Object(2);
  $b = $o;
  $b->val = 3;
  print $o->val; //  echos 3

in PHP4 (assuming var is used instead of public)

  $o = new Object(2);
  $b = $o;
  $b->val = 3;
  print $o->val; //  echos 2

This is cause objects in php5 exist all on there own, that get
referenced to a php variable.


On Tue, Dec 06, 2005 at 05:23:45PM -0500, Alan Pinstein wrote:

Question #1: Is the fact that references to objects in the form
$objRef = &$obj don't bump the refcount of $obj an intended behavior
that can be counted on? If so, cool!

So, now that we have a way to do weak references, we should be able
to implement a reasonable memory management scheme for parent-child
objects.

Normally from the client side the interface should look something like:

$parent = new Parent();
$child = new Child();
$parent->addChild($child);

Ok, i get to the code and well what I mentioned above explains why there is no
need to use the $o = &$object;

If I take your code and run it against one of the latest version's
of php 5.1 i will get a var_dump($child) of:

object(pChild)#2 (1) {
  ["parent"]=>
  object(pParent)#1 (1) {
    ["children"]=>
    array(1) {
      [0]=>
      object(pChild)#2 (1) {
        ["parent"]=>
        object(pParent)#1 (1) {
          ["children"]=>
          array(1) {
            [0]=>
            *RECURSION*
          }
        }
      }
    }
  }
}

Which is what I see as expected results.

Curt.
--
cat .signature: No such file or directory

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