In PHP5 objects are no longer copied when assigned. Instead the object's
handle is assigned (similar to a reference but not quite). So the
behaviour is as expected.
Cheers,
Rob.
On Mon, 2007-10-08 at 21:42 +0100, David Restall - System Administrator
wrote:
> Hi,
>
> I think I have discovered a bug in php5. If I haven't, I've discovered
> a bug in the documentation or a bug in my brain.
>
> php -v :-
>
> PHP 5.2.3 (cli) (built: Jun 26 2007 15:38:48)
> Copyright (c) 1997-2007 The PHP Group
> Zend Engine v2.2.0, Copyright (c) 1998-2007 Zend Technologies
>
> I've attached a code snippet for those that want to save it and try
> running it and it's also pasted here :-
>
> """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
> <?php
>
> class Class_1
> {
> private $Text;
>
> function __construct($Text)
> {
> $this->Text = $Text;
> }
>
> function Set($Text)
> {
> $this->Text = $Text;
> }
>
> function Display()
> {
> print $this->Text . "\n";
> }
> } // End Class_1
>
> class Class_2
> {
> private $Text;
> private $C1;
>
> function __construct($Text)
> {
> $this->Text = $Text;
>
> $this->C1 = new Class_1('From David');
> }
>
> function Set_C1($Text)
> {
> $this->C1->Set($Text);
> }
>
> function Display()
> {
> print $this->Text . "\n";
> $this->C1->Display();
> }
> } // End Class_2
>
> print "Below is T1\n";
>
> $T1 = new Class_1('Hello');
> $T1->Display();
>
> print "Below is T2\n";
> $T2 = new Class_2('World');
> $T2->Display();
>
> print "Copying T2\n";
>
> $T3 = $T2;
>
> print "T2 Copied, original value is :-\n";
>
> $T2->Display();
>
> print "Copy of T2 (T3) value is :- \n";
>
> $T3->Display();
>
> print "Changing T3\n";
>
> $T3->Set_C1("This clears Dave");
>
> print "T3 Change complete, new value is :-\n";
>
> $T3->Display();
>
> print "Below is T2 which shouldn't have changed !!! \n";
>
> $T2->Display();
>
> // var_dump($T1);
>
> ?>
>
> """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
>
> The output it produces is :-
>
> % php -e bug.php
> Below is T1
> Hello
> Below is T2
> World
> >From David
> Copying T2
> T2 Copied, original value is :-
> World
> >From David
> Copy of T2 (T3) value is :-
> World
> >From David
> Changing T3
> T3 Change complete, new value is :-
> World
> This clears Dave
> Below is T2 which shouldn't have changed !!!
> World
> This clears Dave
> %
>
> Now I would expect that $T2 would not change when I changed $T3.
> Reading the documentation :-
>
> <http://www.php.net/manual/en/language.references.whatdo.php>
>
> "... Note: Not using the & operator causes a copy of the object to be
> made. If you use $this in the class it will operate on the current
> instance of the class. The assignment without & will copy the instance
> (i.e. the object) and $this will operate on the copy, which is not
> always what is desired. Usually you want to have a single instance to
> work with, due to performance and memory consumption issues."
>
> This effectively states that $T3 is a 'COPY' of $T2 and $T3 works on the
> copy, not the master yet in the above snippet, the copy and the master
> have both been changed. Further documentation mentions that the copy
> starts off as a reference and only becomes a copy when it is changed.
> This doesn't seem to be happening.
>
> I found this because in my actual application I was using :-
> Master.class
> ...
> $Clone = $this;
>
> $Clone->Do_Something;
>
>
> and later in master.class I did :-
>
> $this->Do_Something_Else
>
> and php barfed with :-
>
> PHP Fatal error: Call to a member function Function_Name() on a non-object
>
> I had deleted the missing object in $Clone but not in the master (this
> was the whole idea of working on $Clone - I didn't want to delete the
> object in the master !!).
>
> I can't find anything similar in the bug database on php.net (but I may
> be looking in the wrong place) and I can't believe that I'm the first
> person to encounter this.
>
> Can anybody explain if this is a bug or if I have misunderstood the
> documentation ?
>
> TTFN
>
>
>
> D
> php/general-2007-10-08.tx php-general
> +----------------------------------------------------------------------------+
> | Dave Restall, Computer Nerd, Cyclist, Radio Amateur G4FCU, Bodger |
> | Mob +44 (0) 7973 831245 Skype: dave.restall Radio: G4FCU |
> | email : dave@xxxxxxxxxxx Web : Not Ready Yet :-( |
> +----------------------------------------------------------------------------+
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> | -- R. E. Schenk |
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