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 = $id;
> > > }
> > >
> > > }
> > >
> > > ?>
> > > end third code snippet --------------------------------
> > >
> > > Well that's it. I hope someone can help me on this. I'm not a person
who
> > > asks for help very quick. I prefer finding it out myself, also because
> I'm
> > > pretty experienced at PHP. But this is the first time I really can't
> figure
> > > out what it is... I really NEEEEED you now :)
> > >
> > > Good luck and a lot of thanks in advance,
> > >
> > > Tim.
> > >
> > > P.S. I'm using PHP4, I do not know this code's reliability and
behaviour
> > > when running it with previous versions.
> > >
> > >
> > > begin 666 complex.php
> > > M/#]P:' -"@T*8VQA<W,@0V]N=&%I;F5R#0I[#0H)#0H)=F%R("1C:&EL9')E
> > > M;CL-"@EV87(@)'!R;W!E<G1Y.PT*#0H)9G5N8W1I;VX@0V]N=&%I;F5R*"1L
> > > M;V%D(#T@1D%,4T4I#0H)>PT*(" @(" @(" D=&AI<RT^<')O<&5R='D@/2 G
> > > M;F]T(&QO861E9"<[#0H)(" @(&EF("@D;&]A9"D@>PT*(" @( D))'1H:7,M
> > > M/FQO860H*3L-"B @(" @(" @?0T*"7T-"@T*(" @(&9U;F-T:6]N(&QO860H
> > > M*0T*(" @('L-"B @(" @(" @)&YE=T-H:6QD(#T@;F5W($-H:6QD*#$I.PT*
> > > M(" @(" @(" D=&AI<RT^861D*"1N97=#:&EL9"D[#0H@(" @(" @("1T:&ES
> > > M+3YP<F]P97)T>2 ]("=S=&%T92 Q)SL-"B @("!]#0H-"@EF=6YC=&EO;B!A
> > > M9&0H)&-H:6QD*0T*"7L-"@D))&-H:6QD+3YP87)E;G0@/2 F)'1H:7,[#0H)
> > > M"21T:&ES+3YC:&EL9" ]("8D8VAI;&0[#0H)?0T*#0H@(" @9G5N8W1I;VX@
> > > M<')I;G13=&%T92@I#0H@(" @>PT*(" @(" @("!P<FEN=" G<')O<&5R='D@
> > > M/2!<)R<@+B D=&AI<RT^<')O<&5R='D@+B G7"<\0E(^)R N#0H@(" @(" @
> > > M(" @(" G8VAI;&0M/G!A<F5N="T^<')O<&5R='D@/2!<)R<@+B D=&AI<RT^
> > > M8VAI;&0M/G!A<F5N="T^<')O<&5R='D@+B G7"<\4#XG.PT*(" @('T-"@D-
> > > M"GT-"@T*8VQA<W,@0VAI;&0-"GL-"@D-"@EV87(@)&ED.PT*"79A<B D<&%R
> > > M96YT.PT*"0T*"69U;F-T:6]N($-H:6QD*"1I9"D-"@E[#0H)"21T:&ES+3YI
> > > M9" ]("1I9#L-"@E]#0H)#0I]#0H-"@T*)'1E<W1#;VYT86EN97(R(#T@;F5W
> > > M($-O;G1A:6YE<BA44E5%*3L-"B1T97-T0V]N=&%I;F5R,BT^<')I;G13=&%T
> > > [EMAIL PROTECTED]*#0HD=&5S=$-O;G1A:6YE<C(M/G!R;W!E<G1Y(#T@)W-T871E(#(G
> > > M.PT*)'1E<W1#;VYT86EN97(R+3YP<FEN=%-T871E*"D[#0H-"G!R:6YT("<\
> > > M2%(^)SL-"@T*)'1E<W1#;VYT86EN97(Q(#T@;F5W($-O;G1A:6YE<CL-"B1T
> > > M97-T0V]N=&%I;F5R,2T^;&]A9"@I.PT*)'1E<W1#;VYT86EN97(Q+3YP<FEN
> > > M=%-T871E*"D[#0H-"B1T97-T0V]N=&%I;F5R,2T^<')O<&5R='D@/2 G<W1A
> > > M=&4@,B<[#0HD=&5S=$-O;G1A:6YE<C$M/G!R:6YT4W1A=&4H*3L-"@T*/SX-
> > > !"@``
> > > `
> > > end
> > >
> > >
> > > --
> > > PHP General Mailing List (http://www.php.net/)
> > > To unsubscribe, visit: http://www.php.net/unsub.php
> > >
> >
> >
>
>
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