with the reference you simply are re-refering the old internal values of the class. No, it is not reccomened to do so, unless, of course, you have a very good reason to.
-- Maxim Maletsky [EMAIL PROTECTED] Martin Towell <[EMAIL PROTECTED]> wrote... : > I remember reading somewhere (can't remember where though, maybe the php.net > web site??) that if you use $this in a constructor (or any methods the > constuctor calls), then you should instantiate the object using &new > otherwise you get a copy of the object that's just been created and not the > actual new object (if that's not too confusing...) > > It's to do with the way the assignment operator works.. > > -----Original Message----- > From: Tim Molendijk [mailto:tawm@;wanadoo.nl] > Sent: Friday, November 08, 2002 4:14 PM > To: [EMAIL PROTECTED] > Subject: Re: [PHP] Weird behaviour with references to objects... > > > Hi all, > > First of all, thank you for the suggestions. > > Actually I accidently found a solution to the problem... Not that I > understand it now, I just found a way to cope with it. By changing the first > line of the first code snippet: > $testContainer1 = new Container(TRUE); > into: > $testContainer1 = &new Container(TRUE); > the problem is gone! > > Don't ask me WHY this is the solution. In my Container->add() method I > assign A REFERENCE of the Container object (&$this) to $child->parent so I > don't see why creating the Container object by reference is useful... > > If anyone has additional information on this subject feel free to post! > > Thanks everyone! > Tim. > > "Mike Mannakee" <[EMAIL PROTECTED]> wrote in message > news:20021108044622.68446.qmail@;pb1.pair.com... > > This sounds like a matter that ought to make it to the programmers who > code > > PHP itself. In the meantime can you code around it now that you know the > > bug is there? > > > > Mike > > > > > > "Marco Tabini" <[EMAIL PROTECTED]> wrote in message > > news:1036725595.21741.868.camel@;localhost.localdomain... > > > I'm not sure if my answer is going to be of much help, but I think this > > > has to do with the way PHP handles references and copies of objects--it > > > uses what I understand is a lazy copy mechanism, and thus the results on > > > object manipulations can yield odd results. There was a discussion on a > > > similar problem on PHP-DEV a while back--if you search the forums you > > > should be able to find it. > > > > > > Hope this helps... > > > > > > > > > Marco > > > ------------- > > > php|architect -- The Monthly Magazine For PHP Professionals > > > Come visit us on the web at http://www.phparch.com! > > > > > > On Thu, 2002-11-07 at 21:36, Tim Molendijk wrote: > > > > First of all I would like to say that I know this is a lot of text but > I > > > > would be very pleased if you take a little time to read it > nevertheless. > > The > > > > situation described below is not complicated at all... > > > > ===================================== > > > > > > > > Hello all, > > > > > > > > I'm dealing with this really weird problem which occurs when dealing > > with > > > > references within objects pointing to other objects. I'm trying to > find > > out > > > > what it is now for a few days and I still don't get it. I minimised > the > > code > > > > around the problem and it's weirder than ever. I would really > appreciate > > it > > > > when you could take a look... I'm pretty experienced at PHP but > perhaps > > you > > > > know something that I don't know. > > > > > > > > We have two different classes: Container and Child. Container objects > > > > contain a Child object in its $child property. A Child object has a > > $parent > > > > property, which contains a *reference* to the Container object by > which > > it > > > > is held. > > > > So $containerObject should be the *same* as > > $containerObject->child->parent. > > > > To test this Container objects have a $property property. When > changing > > this > > > > property the difference between one object and identical/cloned > objects > > > > becomes visible. > > > > > > > > Now take a look at the following code. The indented text is code, the > > rest > > > > are comments. The code for the class Container and class Child are > also > > > > included. Please scroll down or take a look at the attached file. > > > > > > > > begin first code snippet -------------------------------- > > > > <?php > > > > > > > > /* New Container object created. At the same time it sets a Child > object > > in > > > > its $child attribute. (This is indicated by passing TRUE.) */ > > > > $testContainer1 = new Container(TRUE); > > > > /* The Container object is created, the Child object is set and its > > > > reference to the Container object is set. Now it prints > > > > $testContainer1->property and $testContainer->child->parent->property. > > These > > > > should have an identical value because they should be from the same > > object > > > > (not cloned/identical, but the same). > > > > This is the result: > > > > property = 'state 1' > > > > child->parent->property = 'state 1' > > > > So this is as expected, no problem... yet. */ > > > > $testContainer1->printState(); > > > > > > > > /* Now $testContainer1's $property property is changed into another > > value. > > > > /* > > > > $testContainer1->property = 'state 2'; > > > > /* Now $testContainer1->child->parent->property should also have value > > > > 'state 2', but it HAS NOT! > > > > This is the result: > > > > property = 'state 2' > > > > child->parent->property = 'state 1' > > > > Obviously $testContainer1->child->parent->property is not the same > > object as > > > > $testContainer1, but a clone! */ > > > > $testContainer1->printState(); > > > > > > > > ?> > > > > end first code snippet -------------------------------- > > > > > > > > Well, this is the whole problem... Why on earth isn't it a reference, > > while > > > > I really did assign it as a reference in the code (see class code). > > > > > > > > Now to make the whole thing even weirder, take a short look at the > > following > > > > code. It is almost completely the same as above, except that instead > of > > > > giving the Container constructor the command to assign a Child object > to > > the > > > > $child property, this command is given manually by calling method > > load() -- > > > > which is the method that Container constructor uses to load the Child > > > > object. > > > > > > > > begin second code snippet -------------------------------- > > > > <?php > > > > > > > > /* Here the Container object is created again. But now no TRUE is > passed > > > > because we don't want the Container constructor method to create and > > assign > > > > a Child object to the $child property. */ > > > > $testContainer2 = new Container; > > > > /* In the first code snippet load() is called from the Container > > constructor > > > > method. So in fact nothing has changed, except the fact that load() is > > > > called from the client scope instead of the Container object scope > now. > > */ > > > > $testContainer2->load(); > > > > $testContainer2->printState(); > > > > > > > > $testContainer2->property = 'state 2'; > > > > /* After $property has been modified again, $testContainer2's state is > > > > printed again, and now the result is DIFFERENT!!!: > > > > property = 'loaded state 2' > > > > child->parent->property = 'loaded state 2' > > > > This is the CORRECT result!!! This is what we also expected from the > > first > > > > code snippet!!! And this while the executed codes are in fact > > identical!!! > > > > How on earth is this possible?!? */ > > > > $testContainer2->printState(); > > > > > > > > ?> > > > > end second code snippet -------------------------------- > > > > > > > > Well, this is the contradiction I wanted to show you all. I don't see > > the > > > > logics of it all, but ofcourse I could be missing one obvious thing... > > > > actually I hope so, because I need the construction as in the first > code > > > > snippet. > > > > > > > > Below the code for the classes Container en Child. > > > > > > > > begin third code snippet -------------------------------- > > > > <?php > > > > > > > > class Container > > > > { > > > > > > > > var $children; > > > > var $property; > > > > > > > > function Container($load = FALSE) > > > > { > > > > $this->property = 'not loaded'; > > > > if ($load) { > > > > $this->load(); > > > > } > > > > } > > > > > > > > function load() > > > > { > > > > $newChild = new Child(1); > > > > $this->add(&$newChild); > > > > $this->property = 'state 1'; > > > > } > > > > > > > > function add($child) > > > > { > > > > /* Here a reference of $this (the Container object) is assigned to > > $child's > > > > $parent attribute. */ > > > > $child->parent = &$this; > > > > /* Here $child (the newly created Child object) is assigned to the > > > > container's $child property. */ > > > > $this->child = &$child; > > > > } > > > > > > > > function printState() > > > > { > > > > print 'property = \'' . $this->property . '\'<BR>' . > > > > 'child->parent->property = \'' . > > $this->child->parent->property > > > > . '\'<P>'; > > > > } > > > > > > > > } > > > > > > > > class Child > > > > { > > > > > > > > var $id; > > > > var $parent; > > > > > > > > function Child($id) > > > > { > > > > $this->id = $id; > > > > } > > > > > > > > } > > > > > > > > ?> > > > > end third code snippet -------------------------------- > > > > > > > > Well that's it. I hope someone can help me on this. I'm not a person > who > > > > asks for help very quick. I prefer finding it out myself, also because > > I'm > > > > pretty experienced at PHP. But this is the first time I really can't > > figure > > > > out what it is... I really NEEEEED you now :) > > > > > > > > Good luck and a lot of thanks in advance, > > > > > > > > Tim. > > > > > > > > P.S. I'm using PHP4, I do not know this code's reliability and > behaviour > > > > when running it with previous versions. > > > > > > > > > > > > begin 666 complex.php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`` > > > > ` > > > > end > > > > > > > > > > > > -- > > > > PHP General Mailing List (http://www.php.net/) > > > > To unsubscribe, visit: http://www.php.net/unsub.php > > > > > > > > > > > > > > > > > > -- > PHP General Mailing List (http://www.php.net/) > To unsubscribe, visit: http://www.php.net/unsub.php > > -- > PHP General Mailing List (http://www.php.net/) > To unsubscribe, visit: http://www.php.net/unsub.php > -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
