Is it possible to work with pointers in PHP?

Question

So I understand that references aren't pointers: http://php.net/manual/en/language.references.arent.php

Question is, is it possible to work with pointers in php?

Given the following example I would guess that's what we do when working with objects:

class Entity
{
  public $attr;
}

class Filter
{
  public function filter(Entity $entity)
  {
    $entity->attr = trim($entity->attr);
  }
}

$entity = new Entity;
$entity->attr = '  foo  ';
$filter = new Filter;
$filter->filter($entity);
echo $entity->attr; // > 'foo', no white space

Is the example above working with pointers behind the sceen or is it still swapping memory, as when working with references?

Edit

A different example:

Is the following:

class Entity
{
  public $attr;
}
$entity = new Entity;
$entity->attr = 1;
$entity->attr = 2;

Something like this in C :

int* attr;
*attr = 1;
*attr = 2;

Answer 1

When you pass an object as an argument to your function, the variable itself is copied but the properties it has point to those of the original object, ie:

function test(Something $bar)
{
    $bar->y = 'a'; // will update $foo->y
    $bar = 123; // will not update $foo
}

$foo = new Something;
$foo->y = 'b';
test($foo);
// $foo->y == 'a';

Inside the function the memory references look a bit like this:

$bar ---+
        +---> (object [ y => string('b') ])
$foo ---+

After $bar = 123; it looks like this:

$bar ---> int(123)

$foo ---> (object [ y => 'b' ])

Answer 2

If you are asking that in this line

$entity->attr = trim($entity->attr);

the $entity is a new memory or the reference of the old memory. It is the reference of the old memory (or pointer)