[PHP-DOC] #20842 [Fbk->Opn]: No explanation of object comparison and copying From: dparks <email protected>
Date: 12/05/02

 ID: 20842
 User updated by: dparks <email protected>
 Reported By: dparks <email protected>
-Status: Feedback
+Status: Open
 Bug Type: Documentation problem
 Operating System: Any
 PHP Version: 4.2.3
 New Comment:

Argh!! Apparently, PHP evaluates

$this->val = val;

without error, treating val like 'val'. I can't find this documented in
the manual.

The code posted near the end of the bug at
http://bugs.php.net/bug.php?id=20681 (look for [28 Nov 2:02pm]
moriyoshi <email protected>) contains an error like this, which was not noticed
by 4 people. Because of this, the code returns true for all
comparisons.

The behavior you describe is what I expected. Sorry about the mixup.

It would still be nice to have an explanation about how copies
(assignment) are done on objects -- is this a deep value copy? How are
references handled?

Also, it would be nice if the comparison operator page explained how
recursion is handled.

Previous Comments:
------------------------------------------------------------------------

[2002-12-05 19:11:48] jmcastagnetto <email protected>

Can you be more precise about what comparison operations you have in
mind? Remember that PHP is not OOP, it is a language that supports
OOP-style coding, so there is no inherent way of checking if 2
different instances of objects are of the same class w/ the same
properties, or two variables pointing to the same object instance.

The following code generates the expected result:

function bool2str($bool) {
        if ($bool === false) {
                return 'FALSE';
        } else {
                return 'TRUE';
        }
}
class Foo {

        var $flag;

        function Foo($flag=true) {
                $this->flag = $flag;
        }
}

$o = new Foo();
$p = new Foo(false);
$q = new Foo();

// this should be true
echo bool2str($o == $q)."\n";
// this should be false
echo bool2str($o != $q)."\n";
// this should be true
echo bool2str($o === $q)."\n";
// this should be false
echo bool2str($o == $p)."\n";
// this should be false
echo bool2str($o === $p)."\n";
// this should be true
echo bool2str($o != $p)."\n";
// this should be true
echo bool2str($o !== $p)."\n";

------------------------------------------------------------------------

[2002-12-05 16:22:03] dparks <email protected>

I cannot find any explanation of object copying or comparison in the
PHP manual (or in the user comments).

Even a note saying "don't expect comparison operators to work on
objects" would by useful -- it would have saved me a couple of days of
debugging and rewriting code.

------------------------------------------------------------------------ 

-- 
Edit this bug report at http://bugs.php.net/?id=20842&edit=1

-- 
PHP Documentation Mailing List (http://www.php.net/)
To unsubscribe, visit: http://www.php.net/unsub.php