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Bug #61915 incorrect associativity of ternary operator
Submitted: 2012-05-02 22:16 UTC Modified: 2019-04-09 10:21 UTC
From: iam4webwork at hotmail dot com Assigned:
Status: Not a bug Package: Scripting Engine problem
PHP Version: Irrelevant OS: Linux,Windows
Private report: No CVE-ID: None
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 [2012-05-02 22:16 UTC] iam4webwork at hotmail dot com 
Description:
------------
zend_language_parser.y on line 81 gives the '?:' operator left associativity when 
it should be right as in virtually every other language that has a ternary 
operator.  

Test script:
---------------
$arg = "3";
$food = (  ($arg == '1') ? 'Banana' :
           ($arg == '2') ? 'Apple' :
           ($arg == '3') ? 'Toast' :
           ($arg == '4') ? 'Cantalope' :
           ($arg == '5') ? 'Swiss Cheese' : 'Fig Newton Cookie'
		 );
echo $food;

Expected result:
----------------
I expected to see 'Toast'. 

Actual result:
--------------
The actual result is 'Swiss Cheese'.

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 [2012-05-02 22:38 UTC] johannes@php.net 
Yes, this was an oversight when the language was defined and is documentedlike that on http://php.net/ternary (see the last note). Unfortunately we can't fix this without breaking code, which depends on the current order, in a non-obvious way.
 [2012-05-02 22:38 UTC] johannes@php.net
-Status: Open +Status: Not a bug
 [2012-11-12 14:47 UTC] sun at unleashedmind dot com 
Recent major versions of PHP have introduced differences in behavior that are far worse than a correction of the ternary operator associativity would be.

IMHO, correcting this should be seriously considered for PHP 5.5 (or whatever is next ;)), since the current behavior is indeed very unexpected.

If PHP applications need to support older PHP major versions, then a version-agnostic ternary operator logic can be easily achieved through proper usage of parenthesis (which are required to achieve the expected ternary logic today already, right? -- which in turn, further undermines the compatibility argument?).

(Also, based on my experience with other developers who struggled with the current behavior, most of them simply gave up and changed their code to if/else or switch control structures in the first place.)
 [2016-12-16 14:37 UTC] tharkon at gmail dot com 
I am a bit annoyed by the Note a bug status.
It is a bug, you just chose not to fix it.
 [2017-03-21 14:12 UTC] vittorio dot zamparella at gmail dot com 
Php7 would have been a good chance for fixing it, can we hope for Php8?
This is not "a bad feature" programmers can work around, it just requires a useless number of parenthesis that makes code much less clear.

Why not add another operator like "??" with the right associativity? (pun coincidental)
$a ?? $b : $c 

$food = (  ($arg == '1') ?? 'Banana' :
           ($arg == '2') ?? 'Apple' :
           ($arg == '3') ?? 'Toast' :
           ($arg == '4') ?? 'Cantalope' :
           ($arg == '5') ?? 'Swiss Cheese' : 'Fig Newton Cookie'
);
would yeld the (human-brain) expected result without much hassle.

Of course that would bring in Super Elvis ??:
 [2019-04-09 10:21 UTC] bishop@php.net 
RFC "Deprecate left-associative ternary operator"[1] proposes to address this as of PHP 8.

[1]: https://wiki.php.net/rfc/ternary_associativity
 
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