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Bug #49019 order of operations is not valid for assignment in all cases
Submitted: 2009-07-22 17:10 UTC Modified: 2009-07-22 21:53 UTC
From: michaeldnelson dot mdn at gmail dot com Assigned:
Status: Not a bug Package: Scripting Engine problem
PHP Version: 5.2.10 OS: freebsd
Private report: No CVE-ID: None
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From: michaeldnelson dot mdn at gmail dot com
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 [2009-07-22 17:10 UTC] michaeldnelson dot mdn at gmail dot com 
Description:
------------
It appears = has a higher precedence than || in some situations which is contrary to the manual.  This exception is not noted as far as I can tell.

var_dump(!$test = false || !$test2 = false);
is being interpreted like this
var_dump(!$test = (false || !$test2 = false));
instead of like this
var_dump((!$test = false) || (!$test2 = false));

If I missed something my apologies.

Thanks,
Michael D. Nelson

Reproduce code:
---------------
---
From manual page: language.operators.precedence
---
var_dump(!$test = false || !$test2 = false);
echo "TEST\n";
var_dump($test);
echo "TEST2\n";
var_dump($test2);

Expected result:
----------------
bool(true)
TEST
bool(false)
TEST2
NULL

Actual result:
--------------
bool(false)
TEST
bool(true)
TEST2
bool(false)

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 [2009-07-22 20:15 UTC] jani@php.net 
= is associated on right, || is associated on left, so that's exactly 
what your code does..
 [2009-07-22 21:00 UTC] michaeldnelson dot mdn at gmail dot com 
Thank you for the prompt response at the risk of proving myself more obtuse:
 
I am aware of how = and || are associated it would appear to me that if || is associated on the left and it is associated before any = then (!$test = false || !$test2 = false) should evaluate to true because the left portion of this is just (!$test = false) which  evaluates to true, also (!$test = false || false) evaluates to true if you meant that the false immediately to the left was causing this result this case proves otherwise.
 
It still appears to me that ($!test = false || $!test2 = false) evaluates to false because the leftmost = operator is getting evaluated before the ||.  I apologize for taking more of your time but your terse response didn't assuage my doubts on this particular issue, perhaps if you elaborated. Thanks again.)
 [2009-07-22 21:25 UTC] jani@php.net 
You propably also missed the fine print:

"Note: Although = has a lower precedence than most other operators, PHP 
will still allow expressions similar to the following: if (!$a = foo()), 
in which case the return value of foo() is put into $a. "

So what you get is quite expected. No bug here.
 [2009-07-22 21:53 UTC] michaeldnelson dot mdn at gmail dot com 
I read that I assumed
if (!$a = foo()) this note was in reference to the ! operators precedence where $a should be as of yet unassigned.

Thank you for your time.

Michael D. Nelson)
 
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