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	 <1246545959-sup-2910@javelin>
Date: Thu, 2 Jul 2009 16:55:48 +0200
Message-ID: <98b8086f0907020755k1c29930n8a4cef38dbb61291@mail.gmail.com>
To: internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] constructors are callable as regular functions.
From: troelskn@gmail.com (troels knak-nielsen)

On Thu, Jul 2, 2009 at 4:47 PM, Edward Z. Yang<ezyang@mit.edu> wrote:
> Excerpts from troels knak-nielsen's message of Thu Jul 02 10:14:18 -0400 =
2009:
>> I would have expected the second call to __construct() to yield an error=
.
>
> Why should it? Especially since this is idiomatic code:
>
> class A {
> =A0public function __construct($a) {
> =A0 =A0$this->a =3D $a;
> =A0}
> }
>
> class B extends A {
> =A0public function __construct($a, $b) {
> =A0 =A0$this->b =3D $b;
> =A0 =A0parent::__construct($a);
> =A0}
> }

In that example, the object instance is not initialised when
parent::__construct() is called.

> __construct doesn't do anything like allocate memory. It just happens
> to get called when we do "new B(1, 2)"

I understand that. It's not a technical issue - It's more a matter of
language semantics. Constructors are used for initializing state on an
object. Basically, this behaviour makes it impossible to implement
immutable objects in php. It's not a huge deal - I don't remember ever
seen __construct() called directly.

--
troels