Question

I am creating a linklist class and have some confusion about reference to objects.

As per my understanding by default object is copied by reference. $Obj1 = $Obj2. $Obj1 is a alias of $Obj2.

Can someone please point out which one is correct in linkedlist implementation.

$firstNode->next = $this->first;---> seems to be correct
             or 
$firstNode->next =& $this->first;

$this->first = $firstNode;-----> seems to be correct as $firstNode is an object
             or 
$this->first = & $firstNode;

code:

class Node {
    public $element;
    public $next;

public function __construct($element){
    $this->element = $element;
    $this->next = NULL;
  }
}

class Linklist {

    private $first;
    private $listSize;

 public function __construct(){      
    $this->first = NULL;
    $this->listSize = 0;
}

public function InsertToFirst($element){
     $firstNode = new Node($element);
     $firstNode->next = $this->first;   // or $firstNode->next =& $this->first;
     $this->first = $firstNode;  // or $this->first = & $firstNode;
 }

Answer 1

In PHP you do not need to use reference assignment (aliasing/&) for your linked list if each node is an object itself and next and first are objects of that node-type as well.

See Objects and References in the PHP Manual to understand the details.