Class new vs &new

[Kold]

Hi.

What does the '&' do when placed in front of new?

e.g.

$myClass = new Game;
and
$myClass = &new Game;

Thanks.
K.

[ahundiak]

The easy answer is to upgrade to php5 and & goes away for objects.

A slightly more complex answer is that even in php4, the two statements are effectivily identical for 99.99% of the classes you might run across so it's not worth worrying about.

If you really want to know when the statements could yield different results then try the manual:
http://www.php.net/manual/en/language.oop.newref.php

Bottom line is that $myClass = new Game actually creates a copy of the object just constructed while $myClass =& new Game does not.

I'd suggest not using the & since php5 no longer needs it.

[Kold]

Ah, references, of course - and yes they will not affect what I am doing!

Thanks!
K.

[rvdavid]

Kold wrote:

What does the '&' do when placed in front of new?

e.g.

$myClass = new Game;
and
$myClass = &new Game;

There's a big difference between the two methods of instantiation.

Here's a link that covers your questions regarding this matter.
http://www.sitepoint.com/article/object-oriented-php/7

Regards,

[ahundiak]

rvdavid wrote:

There's a big difference between the two methods of instantiation.

Here's a link that covers your questions regarding this matter.
http://www.sitepoint.com/article/object-oriented-php/7

Regards,

Actually, as I explained in my first post, there is seldom any difference between the two methods as far as functionality goes. Your code runs the same regardless except in a few specific cases.

Your link merely recommends using & to prevent a copy being made. I recommend not using & since when you do do move to php5 you will need to go through and delete all the &'s.

Your link barely touches on the constructor issues and does not even mention the fact that sometimes you have to use & to get the expected behaviour.

[rvdavid]

Your link merely recommends using & to prevent a copy being made. I recommend not using & since when you do do move to php5 you will need to go through and delete all the &'s.

"merely" ? You're either downplaying the importance of instantiating by reference or you do not fully understand the consequences that come of instantiating by copy.

First thing's first however...

Three things

1: I did not claim for the link I posted to be a comprehensive guide to the reference operator. It's merely a piece in the puzzle.

2: I feel what I posted answered the thread author's question. That was enough for me.
He asked, the link I posted answered the question.

What does the '&' do when placed in front of new?

e.g.

$myClass = new Game;
and
$myClass = &new Game;

3: More importantly. I disagree with your recommendation. ... with a passion!
... ok maybe not with a passion, but with lukewarm sentiment. 😃

What you are suggesting will have the following effects.

Consider this code excerpt:

$myObject = new Phone();

There are three things happening here.

The "new Phone()" statement creates an instance of a Phone object.
You then copy the Phone object to the $myObject variable.
The first instance of the phone object is then deleted from memory.

Now consider this code exceprt:

$myObject =& new Phone();

The "new Phone()" statement creates an instance of a Phone object.
The $myObject variable points/refers to the original instance of the Phone object.

There's a big difference between the two.
To add to this, consider the following classes:

class Web_Ring {

var $_website;

function load_site(&$website) {
    $this->_website = &$website;
}

function display() {
    $this->_website->output();
}
}

class Website 
{

var $_data;

function Website(&$portal) {
    $portal->load_site($this);
}

function set_data($data) {
    $this->_data = $data;
}

function output() {
    print $this->_data;
}
}

This implementation will display the correct information.

$web_ring = &new Web_Ring();
$website = &new Website($web_ring); // using the reference operator.
$website->set_data('This is a virtual website which is part of a web ring');
$web_ring->display(); // displays 'This is a virtual website which is part of a web ring'

This will not display anything.

$web_ring = &new Web_Ring();
$website = new Website($web_ring); // no reference operator
$website->set_data('This is a virtual website which is part of a web ring');
$web_ring->display();  // displays nothing

With regards to PHP5 migration, a quick search and replace would fix your problem.
Search for "=& new" replace with "= new".

I could give you a whole migration strategy, but I'll stop here. 😉

Hope this clears some things up for you.

Regards,