#29441 [Bgs]: After copying a class, changes to new class affect old class.
ID: 29441
User updated by: php at cyruslesser dot com
Reported By: php at cyruslesser dot com
Status: Bogus
Bug Type: Class/Object related
Operating System: *
PHP Version: 5.*
New Comment:
BTW, for anyone else reading this who also had trouble finding the
documention, check this URL which is details the changes in the Zend 2
engine:
http://www.php.net/zend-engine-2.php
Specifically, the solution to my problem was very simple:
$new_object = clone $old_object;
Although I still feel that always forcing passing objects by reference
to functions is a bit silly, I'm willing to live with it for the sake
of the many great improvements to PHP5.
Thanks.
Cyrus
Previous Comments:
[2004-08-03 03:38:32] [EMAIL PROTECTED]
http://zend.com/manual/migration5.oop.php
scroll down to "Objects Cloning"
[2004-08-03 03:30:50] php at cyruslesser dot com
Sorry, that was supposed to read "ARE THERE new functions to aid in the
duplication of objects by value?"
Cyrus
----
[2004-08-03 03:26:24] php at cyruslesser dot com
Yes, why must everyone I ask about this point out the blatantly obvious
when I ask about this? :)
It's passing classes by reference (or pointer if you prefer the C
analog) not by value. I get it. Honestly I do. I just don't get
why.
Please, is there a way I can quickly copy an object? Where is
memcpy()? Why can't I call clone() directly? Are the new functions to
aid in the duplication of objects by value?
I'm assuming that they do exist, and that I just don't know about them.
I have faith in you guys... your language is the easiest and most
intuitive language I have ever seen, and I love it.
But what I do not understand why you have chosen to do this, or how it
aids the language.
I appreciate that copying a pointer (or reference) to a class is
somewhat quicker than copying the entire object itself, but I don't
really see how duplicating pointers is more useful that duplicating
complete copies of the object.
I just don't think that a small time saving (surely it's just a few
memcpy() calls) is worth the extra time it now takes when you wish to
duplicate an object. Or the problems this is going to cause with PHP4
software running under PHP5.
In PHP5, if I have an object containing data retrieved from a database,
and I want to copy it, I have to instantiate a new object, and either
repeat all the calls to the database to retrieve the data, or copy
every member variable individually to the new class.
Either way it's slow and tedious. But I'm very hopeful that there is
a new object copy function that wasn't in the PHP5 "what's new"
documentation.
I have to say, even C++ will automatically copy the contents of a class
unless you override the assignment operator.
Another irksome factor about this whole thing, is the inconsistency
that this brings to the language.
Previously a string object could be treated identically to a class
object.
$string1 = "a";
$string2 = $string1;
$string2 = "b";
Which of course, will leave $string1 == "a".
But if they where class objects, then the behavior suddenly changes,
and $string1 is changed.
This is going to be very confusing to people who have never learnt a
lower-level OO language before.
Even in C++ (which I would regard by todays standard, as a pretty hard
language to learn), strings and class objects behave in the same fashion
when assigned, or used as arguments to functions.
While we're on the topic of functions:
In PHP4:
function ($object) { /* pass by value */
/* This doesn't change the original object */
$object->change();
}
function (&$object) { /* pass by reference */
/* This DOES change the original object */
$object->change();
}
That made sense. There are two different ways to pass an object, and
you can chose which one you wish to use in the declaration of the
function, using '&'.
In PHP5, both of those function have the same effect, they both modify
the original object which is now always passed by reference.
Is this the way it's going to stay?
Cyrus Lesser
[2004-08-02 18:24:11] [EMAIL PROTECTED]
You don't copy a class, you copy an instance.
And since PHP 5.0.0 you no longer copy by value but instead by object
id.
[2004-08-02 14:21:08] php at cyruslesser dot com
Well, in version 4.3.8, it returns
a: 1
b: 2
In version 5.0.0 it returns (without error or notificatio
#29441 [Bgs]: After copying a class, changes to new class affect old class.
ID: 29441
User updated by: php at cyruslesser dot com
Reported By: php at cyruslesser dot com
Status: Bogus
Bug Type: Class/Object related
Operating System: *
PHP Version: 5.*
New Comment:
Sorry, that was supposed to read "ARE THERE new functions to aid in the
duplication of objects by value?"
Cyrus
Previous Comments:
[2004-08-03 03:26:24] php at cyruslesser dot com
Yes, why must everyone I ask about this point out the blatantly obvious
when I ask about this? :)
It's passing classes by reference (or pointer if you prefer the C
analog) not by value. I get it. Honestly I do. I just don't get
why.
Please, is there a way I can quickly copy an object? Where is
memcpy()? Why can't I call clone() directly? Are the new functions to
aid in the duplication of objects by value?
I'm assuming that they do exist, and that I just don't know about them.
I have faith in you guys... your language is the easiest and most
intuitive language I have ever seen, and I love it.
But what I do not understand why you have chosen to do this, or how it
aids the language.
I appreciate that copying a pointer (or reference) to a class is
somewhat quicker than copying the entire object itself, but I don't
really see how duplicating pointers is more useful that duplicating
complete copies of the object.
I just don't think that a small time saving (surely it's just a few
memcpy() calls) is worth the extra time it now takes when you wish to
duplicate an object. Or the problems this is going to cause with PHP4
software running under PHP5.
In PHP5, if I have an object containing data retrieved from a database,
and I want to copy it, I have to instantiate a new object, and either
repeat all the calls to the database to retrieve the data, or copy
every member variable individually to the new class.
Either way it's slow and tedious. But I'm very hopeful that there is
a new object copy function that wasn't in the PHP5 "what's new"
documentation.
I have to say, even C++ will automatically copy the contents of a class
unless you override the assignment operator.
Another irksome factor about this whole thing, is the inconsistency
that this brings to the language.
Previously a string object could be treated identically to a class
object.
$string1 = "a";
$string2 = $string1;
$string2 = "b";
Which of course, will leave $string1 == "a".
But if they where class objects, then the behavior suddenly changes,
and $string1 is changed.
This is going to be very confusing to people who have never learnt a
lower-level OO language before.
Even in C++ (which I would regard by todays standard, as a pretty hard
language to learn), strings and class objects behave in the same fashion
when assigned, or used as arguments to functions.
While we're on the topic of functions:
In PHP4:
function ($object) { /* pass by value */
/* This doesn't change the original object */
$object->change();
}
function (&$object) { /* pass by reference */
/* This DOES change the original object */
$object->change();
}
That made sense. There are two different ways to pass an object, and
you can chose which one you wish to use in the declaration of the
function, using '&'.
In PHP5, both of those function have the same effect, they both modify
the original object which is now always passed by reference.
Is this the way it's going to stay?
Cyrus Lesser
[2004-08-02 18:24:11] [EMAIL PROTECTED]
You don't copy a class, you copy an instance.
And since PHP 5.0.0 you no longer copy by value but instead by object
id.
[2004-08-02 14:21:08] php at cyruslesser dot com
Well, in version 4.3.8, it returns
a: 1
b: 2
In version 5.0.0 it returns (without error or notification)
a: 2
b: 2
That may or may not be intentional, but if there's a way to copy an
object instead of a pointer to an object, I can't find it in the
manual.
Cyrus Lesser
[2004-08-02 12:56:01] [EMAIL PROTECTED]
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php
.
[2004-07-29 08:44:27] php at cyruslesser dot com
Description:
This may just be my mis-understanding of how the language should work,
but surely when you copy an object (class) and make changes to it,
those changes shouldn't affect
#29441 [Bgs]: After copying a class, changes to new class affect old class.
ID: 29441
User updated by: php at cyruslesser dot com
Reported By: php at cyruslesser dot com
Status: Bogus
Bug Type: Class/Object related
Operating System: *
PHP Version: 5.*
New Comment:
Yes, why must everyone I ask about this point out the blatantly obvious
when I ask about this? :)
It's passing classes by reference (or pointer if you prefer the C
analog) not by value. I get it. Honestly I do. I just don't get
why.
Please, is there a way I can quickly copy an object? Where is
memcpy()? Why can't I call clone() directly? Are the new functions to
aid in the duplication of objects by value?
I'm assuming that they do exist, and that I just don't know about them.
I have faith in you guys... your language is the easiest and most
intuitive language I have ever seen, and I love it.
But what I do not understand why you have chosen to do this, or how it
aids the language.
I appreciate that copying a pointer (or reference) to a class is
somewhat quicker than copying the entire object itself, but I don't
really see how duplicating pointers is more useful that duplicating
complete copies of the object.
I just don't think that a small time saving (surely it's just a few
memcpy() calls) is worth the extra time it now takes when you wish to
duplicate an object. Or the problems this is going to cause with PHP4
software running under PHP5.
In PHP5, if I have an object containing data retrieved from a database,
and I want to copy it, I have to instantiate a new object, and either
repeat all the calls to the database to retrieve the data, or copy
every member variable individually to the new class.
Either way it's slow and tedious. But I'm very hopeful that there is
a new object copy function that wasn't in the PHP5 "what's new"
documentation.
I have to say, even C++ will automatically copy the contents of a class
unless you override the assignment operator.
Another irksome factor about this whole thing, is the inconsistency
that this brings to the language.
Previously a string object could be treated identically to a class
object.
$string1 = "a";
$string2 = $string1;
$string2 = "b";
Which of course, will leave $string1 == "a".
But if they where class objects, then the behavior suddenly changes,
and $string1 is changed.
This is going to be very confusing to people who have never learnt a
lower-level OO language before.
Even in C++ (which I would regard by todays standard, as a pretty hard
language to learn), strings and class objects behave in the same fashion
when assigned, or used as arguments to functions.
While we're on the topic of functions:
In PHP4:
function ($object) { /* pass by value */
/* This doesn't change the original object */
$object->change();
}
function (&$object) { /* pass by reference */
/* This DOES change the original object */
$object->change();
}
That made sense. There are two different ways to pass an object, and
you can chose which one you wish to use in the declaration of the
function, using '&'.
In PHP5, both of those function have the same effect, they both modify
the original object which is now always passed by reference.
Is this the way it's going to stay?
Cyrus Lesser
Previous Comments:
[2004-08-02 18:24:11] [EMAIL PROTECTED]
You don't copy a class, you copy an instance.
And since PHP 5.0.0 you no longer copy by value but instead by object
id.
[2004-08-02 14:21:08] php at cyruslesser dot com
Well, in version 4.3.8, it returns
a: 1
b: 2
In version 5.0.0 it returns (without error or notification)
a: 2
b: 2
That may or may not be intentional, but if there's a way to copy an
object instead of a pointer to an object, I can't find it in the
manual.
Cyrus Lesser
[2004-08-02 12:56:01] [EMAIL PROTECTED]
Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php
.
[2004-07-29 08:44:27] php at cyruslesser dot com
Description:
This may just be my mis-understanding of how the language should work,
but surely when you copy an object (class) and make changes to it,
those changes shouldn't affect the original object?
I don't really see the point in making a copy of an object, if the
changes you make to the new copy affect the old copy.
If I'm just dumb, then I apologise.
Reproduce code:
#29441 [Bgs]: After copying a class, changes to new class affect old class.
ID: 29441 User updated by: php at cyruslesser dot com Reported By: php at cyruslesser dot com Status: Bogus Bug Type: Class/Object related Operating System: Linux Debian PHP Version: 5.0.0 New Comment: Well, in version 4.3.8, it returns a: 1 b: 2 In version 5.0.0 it returns (without error or notification) a: 2 b: 2 That may or may not be intentional, but if there's a way to copy an object instead of a pointer to an object, I can't find it in the manual. Cyrus Lesser Previous Comments: [2004-08-02 12:56:01] [EMAIL PROTECTED] Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.php.net/manual/ and the instructions on how to report a bug at http://bugs.php.net/how-to-report.php . [2004-07-29 08:44:27] php at cyruslesser dot com Description: This may just be my mis-understanding of how the language should work, but surely when you copy an object (class) and make changes to it, those changes shouldn't affect the original object? I don't really see the point in making a copy of an object, if the changes you make to the new copy affect the old copy. If I'm just dumb, then I apologise. Reproduce code: --- i = 1; $b = $a; $b->i = 2; echo "a: $a->i"; echo "b: $b->i"; ?> Expected result: a: 1 b: 2 Actual result: -- a: 2 b: 2 -- Edit this bug report at http://bugs.php.net/?id=29441&edit=1
#29441 [NEW]: After copying a class, changes to new class affect old class.
From: php at cyruslesser dot com Operating system: Linux Debian PHP version: 5.0.0 PHP Bug Type: Class/Object related Bug description: After copying a class, changes to new class affect old class. Description: This may just be my mis-understanding of how the language should work, but surely when you copy an object (class) and make changes to it, those changes shouldn't affect the original object? I don't really see the point in making a copy of an object, if the changes you make to the new copy affect the old copy. If I'm just dumb, then I apologise. Reproduce code: --- i = 1; $b = $a; $b->i = 2; echo "a: $a->i"; echo "b: $b->i"; ?> Expected result: a: 1 b: 2 Actual result: -- a: 2 b: 2 -- Edit bug report at http://bugs.php.net/?id=29441&edit=1 -- Try a CVS snapshot (php4): http://bugs.php.net/fix.php?id=29441&r=trysnapshot4 Try a CVS snapshot (php5): http://bugs.php.net/fix.php?id=29441&r=trysnapshot5 Fixed in CVS: http://bugs.php.net/fix.php?id=29441&r=fixedcvs Fixed in release: http://bugs.php.net/fix.php?id=29441&r=alreadyfixed Need backtrace: http://bugs.php.net/fix.php?id=29441&r=needtrace Need Reproduce Script: http://bugs.php.net/fix.php?id=29441&r=needscript Try newer version: http://bugs.php.net/fix.php?id=29441&r=oldversion Not developer issue:http://bugs.php.net/fix.php?id=29441&r=support Expected behavior: http://bugs.php.net/fix.php?id=29441&r=notwrong Not enough info:http://bugs.php.net/fix.php?id=29441&r=notenoughinfo Submitted twice:http://bugs.php.net/fix.php?id=29441&r=submittedtwice register_globals: http://bugs.php.net/fix.php?id=29441&r=globals PHP 3 support discontinued: http://bugs.php.net/fix.php?id=29441&r=php3 Daylight Savings: http://bugs.php.net/fix.php?id=29441&r=dst IIS Stability: http://bugs.php.net/fix.php?id=29441&r=isapi Install GNU Sed:http://bugs.php.net/fix.php?id=29441&r=gnused Floating point limitations: http://bugs.php.net/fix.php?id=29441&r=float
