Bug #53117 [Bgs]: Assignment by reference within assignment operator
Edit report at http://bugs.php.net/bug.php?id=53117&edit=1
ID: 53117
Updated by: cataphract@php.net
Reported by: dukeofgaming at gmail dot com
Summary: Assignment by reference within assignment operator
Status: Bogus
Type: Bug
Package: *Compile Issues
Operating System: Any (Windows 7)
PHP Version: 5.2.14
Block user comment: N
New Comment:
It's not deprecated. What's deprecated is "=& new something()".
The documentation page for "Assignment operators" talks briefly about
"=&", but it could use some improvements (it even includes the somewhat
inaccurate statement that in PHP 5 objects are assigned by reference).
Previous Comments:
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[2010-10-21 00:57:30] dukeofgaming at gmail dot com
Hi again,
Thanks for the detailed follow-up. I did not have the slightest idea
that this
form of using '&' was deprecated. If '=&' is formally an operator,
shouldn't it be
in the "Assignment Operators" section of the documentation?.
Regards
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[2010-10-21 00:39:15] cataphract@php.net
> I am not under the impresion that there is an asign-by-reference
> operator as such, since one is free to separate "=" from "&", where
> "&" indicates return by reference.
Not really. See the parser definitions here:
http://lxr.php.net/xref/PHP_5_3/Zend/zend_language_parser.y#expr_without_variable
The only (non-deprecated) form of an assignment by reference is:
variable '=' '&' variable { zend_check_writable_variable(&$1);
zend_do_end_variable_parse(&$4, BP_VAR_W, 1 TSRMLS_CC);
zend_do_end_variable_parse(&$1, BP_VAR_W, 0 TSRMLS_CC);
zend_do_assign_ref(&$$, &$1, &$4 TSRMLS_CC); }
The fact you can separate "=" and "&" is maybe unfortunate, because it
causes the sort of confusion you have. Although "&" is used in several
similar contexts (pass by reference, return by reference, assign by
reference, include reference in array expression) and they all share a
common implementation pattern (what in PHP is sadly called "references",
which is actually just a "no copy flag"), they are still conceptually
different processes, with some dissimilarities.
In particular, in PHP there are different opcodes for assignment
(operator =) and assignment by reference (operator =&). To assign by
reference, you don't need just a "reference" (a variable that has the
is_ref no copy flag) or something from which we can extract a reference
on the right hand side, we need to actually use the "assign by
reference" operator.
Consider:
$a =& $b;
$c = $a; //not an assignment by reference, but $a is a "reference".
function &h() { return $GLOBALS['b']; }
$c = h(); //not an assignment by reference, but h() returns by reference
------------------------------------------------------------------------
[2010-10-20 23:24:28] dukeofgaming at gmail dot com
I am not under the impresion that there is an asign-by-reference
operator as such,
since one is free to separate "=" from "&", where "&"
indicates return
by
reference. However the expression part makes this clear.
Regards,
David Vega
------------------------------------------------------------------------
[2010-10-20 22:15:12] cataphract@php.net
This is not a bug. The ternary operator defines an expression. Even if
it allowed yielding a reference (it doesn't), you are not assigning by
reference in
$my_var = ...
The assign by reference operator is "=&", not "=".
------------------------------------------------------------------------
[2010-10-20 18:53:06] dukeofgaming at gmail dot com
Description:
------------
Hi,
PHP throws a fatal error when code like this is processed:
$my_var = (true)?(&$some_obj):(&$some_other_obj->some_arr_pop[]);
Which is not a problem if put like this of course:
$my_var;
if(true){
$my_var = &$some_obj;
}else{
$my_var = &$some_other_obj->some_arr_pop[];
}
Affects both PHP 5.2.x and 5.3.x
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