For a property declared outside of constructor, is it overkill to initalize its value to null inside the constructor?
<p>I was looking at this implementation of a single linked list and noticed that inside the constructor the property <code>$this-&gt;next</code> is set to <code>null</code>.</p>

<p><a href="http://code.activestate.com/recipes/576498-implementation-of-a-single-linked-list-in-php/" rel="nofollow">http://code.activestate.com/recipes/576498-implementation-of-a-single-linked-list-in-php/</a></p>

<p>Since php automatically sets the value of the property <code>$next</code> to <code>null</code> when it is declared outside of the constructor (ex <code>public $next</code>), isn't the line of code <code>$this-&gt;next = NULL</code> overkill?</p>

<pre><code>class ListNode
{
    public $data;
    public $next;

    function __construct($data)
    {
        $this-&gt;data = $data;
        $this-&gt;next = NULL;
    }

    function readNode()
    {
        return $this-&gt;data;
    }
}
</code></pre>

<p>Also - I've seen this convention be used several times in php OOP.  Is this a required convention in some other language?</p>
