in PHP 5, $obj1 = $obj2 not the same as $obj1 =& $obj2

[Summercool]

seems like in PHP 5, $obj1 = $obj2 is not the same as $obj1 =& $obj2

although the manual says...

http://www.php.net/manual/en/languag...assignment.php

Since PHP 4, assignment by reference has been supported,
using the $var = &$othervar

As of PHP 5, objects are assigned by reference
unless explicitly told otherwise with the new clone
keyword.

However, $obj1 = $obj2
and $obj1 = &$obj2 are two different things...

the first one is "assignment by reference"
the second one is "assignment by synonym"

----------------- assign1.php ---------------------

<?php

class Foo {
var $name;

function Foo($i) {
$this->name = "I'm $i!\n";
}
}

$a = new Foo("ha");
$b = $a;
$b = new Foo("hee");

echo "This is php ", phpversion(), "\n\n";
print_r($a);
print_r($b);

?>

----------------- output

This is php 5.2.4

Foo Object
(
[name] =I'm ha!

)
Foo Object
(
[name] =I'm hee!

)
----------------- assign2.php ---------------------

<?php

class Foo {
var $name;

function Foo($i) {
$this->name = "I'm $i!\n";
}
}

$a = new Foo("ha");
$b = &$a;
$b = new Foo("hee");

echo "This is php ", phpversion(), "\n\n";
print_r($a);
print_r($b);

?>

----------------- output

This is php 5.2.4

Foo Object
(
[name] =I'm hee!

)
Foo Object
(
[name] =I'm hee!

)

[gosha bine]

Summercool wrote:

seems like in PHP 5, $obj1 = $obj2 is not the same as $obj1 =& $obj2

although the manual says...

http://www.php.net/manual/en/languag...assignment.php

>Since PHP 4, assignment by reference has been supported,
using the $var = &$othervar

>As of PHP 5, objects are assigned by reference
unless explicitly told otherwise with the new clone
keyword.

The manual is incorrect at this point. Object variables in php5 are
assigned by value, just like in php4, but this very value is different
in php5 - it's a pointer to the object, not the object itself. But this
is essentially another story and has nothing to do with references.
--
gosha bine

extended php parser ~ http://code.google.com/p/pihipi
blok ~ http://www.tagarga.com/blok

[Summercool]

On Sep 27, 8:43 am, gosha bine <[e-mail]:

The manual is incorrect at this point. Object variables in php5 are
assigned by value, just like in php4, but this very value is different
in php5 - it's a pointer to the object, not the object itself. But this
is essentially another story and has nothing to do with references.

--
gosha bine

i think pointer and reference are the same thing, like in Java and
Ruby.
In PHP, what the manual calls "reference" is actually not a reference
in other languages... it is like an alias or (a nickname).

[ZeldorBlat]

On Sep 27, 12:12 pm, Summercool <[e-mail]:

>
i think pointer and reference are the same thing, like in Java and
Ruby.
In PHP, what the manual calls "reference" is actually not a reference
in other languages... it is like an alias or (a nickname).

Correct -- it is a "symbol table alias."

>From the manual:

"References in PHP are a means to access the same variable content by
different names. They are not like C pointers; instead, they are
symbol table aliases. Note that in PHP, variable name and variable
content are different, so the same content can have different names."

Personally I think that's much simpler than the reference model in
other languages.

Also be aware of the distinction between "passing by reference" (as
in, passing to a function) and assigning references.

[gosha bine]

Summercool wrote:

On Sep 27, 8:43 am, gosha bine <[e-mail]:

>The manual is incorrect at this point. Object variables in php5 are
assigned by value, just like in php4, but this very value is different
in php5 - it's a pointer to the object, not the object itself. But this
is essentially another story and has nothing to do with references.

--
gosha bine

i think pointer and reference are the same thing, like in Java and
Ruby.

The term "reference" can be used in the generic sense, describing a
value that is used to access another value. In this sense, a pointer is
a (kind of) reference. However, in c++ and php the word "reference" has
another meaning, and describes some specific construct, that has nothing
to do with pointers. Object variables in php5 are pointers and not
references (in c++/php sense).

In PHP, what the manual calls "reference" is actually not a reference
in other languages... it is like an alias or (a nickname).

Good that you understand this. It means your original problem is cleared
up. ;)

--
gosha bine

extended php parser ~ http://code.google.com/p/pihipi
blok ~ http://www.tagarga.com/blok

[Summercool]

On Sep 27, 8:43 am, gosha bine <[e-mail]:

Summercool wrote:

The manual is incorrect at this point. Object variables in php5 are
assigned by value, just like in php4, but this very value is different
in php5 - it's a pointer to the object, not the object itself. But this
is essentially another story and has nothing to do with references.

I just wonder if the manual is incorrect equating PHP4's =& to
PHP5's obj1 = obj2, then how come it is still there on the website
for so long... and for the whole PHP user audience...

[Summercool]

On Sep 27, 8:43 am, gosha bine <[e-mail]:

gosha bine

extended php parser ~http://code.google.com/p/pihipi
blok ~http://www.tagarga.com/blok

do you work for Google? is the PiHiPi pretty good?

[gosha bine]

Summercool wrote:

On Sep 27, 8:43 am, gosha bine <[e-mail]:

>Summercool wrote:

>The manual is incorrect at this point. Object variables in php5 are
assigned by value, just like in php4, but this very value is different
in php5 - it's a pointer to the object, not the object itself. But this
is essentially another story and has nothing to do with references.

I just wonder if the manual is incorrect equating PHP4's =& to
PHP5's obj1 = obj2, then how come it is still there on the website
for so long... and for the whole PHP user audience...

I'm wondering that too. I consider this wording quite harmful because
I've seen many people confused by the idea that php5 objects have
anything to do with references.
--
gosha bine

extended php parser ~ http://code.google.com/p/pihipi
blok ~ http://www.tagarga.com/blok

[gosha bine]

Summercool wrote:

On Sep 27, 8:43 am, gosha bine <[e-mail]:

>gosha bine

extended php parser ~http://code.google.com/p/pihipi
blok ~http://www.tagarga.com/blok

do you work for Google? is the PiHiPi pretty good?

no, yes
--
gosha bine

extended php parser ~ http://code.google.com/p/pihipi
blok ~ http://www.tagarga.com/blok

[Jerry Stuckle]

Summercool wrote:

On Sep 27, 8:43 am, gosha bine <[e-mail]:

>The manual is incorrect at this point. Object variables in php5 are
assigned by value, just like in php4, but this very value is different
in php5 - it's a pointer to the object, not the object itself. But this
is essentially another story and has nothing to do with references.

--
gosha bine

i think pointer and reference are the same thing, like in Java and
Ruby.
In PHP, what the manual calls "reference" is actually not a reference
in other languages... it is like an alias or (a nickname).

No, pointer and reference are NOT the same thing. It's a common
misconception which screws a lot of people up when the difference is
important.

--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
js*******@attglobal.net
==================

[Jerry Stuckle]

gosha bine wrote:

Summercool wrote:

>On Sep 27, 8:43 am, gosha bine <[e-mail]:

>>The manual is incorrect at this point. Object variables in php5 are
assigned by value, just like in php4, but this very value is different
in php5 - it's a pointer to the object, not the object itself. But this
is essentially another story and has nothing to do with references.

--
gosha bine

i think pointer and reference are the same thing, like in Java and
Ruby.

Not at all. I don't know about Ruby, but Java doesn't have pointers.

The term "reference" can be used in the generic sense, describing a
value that is used to access another value. In this sense, a pointer is
a (kind of) reference. However, in c++ and php the word "reference" has
another meaning, and describes some specific construct, that has nothing
to do with pointers. Object variables in php5 are pointers and not
references (in c++/php sense).

And that thinking really screws people up when the difference is important.

It's like an integer 1 and floating point 1.0. In many cases it's fine.
But not always.

>In PHP, what the manual calls "reference" is actually not a reference
in other languages... it is like an alias or (a nickname).

Good that you understand this. It means your original problem is cleared
up. ;)

--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
js*******@attglobal.net
==================