Edit report at https://bugs.php.net/bug.php?id=60694&edit=1
ID: 60694
Comment by: phpmpan at mpan dot pl
Reported by: MarkAndrewSlade at gmail dot com
Summary: print() results in bad logic
Status: Open
Type: Bug
Package: Scripting Engine problem
Operating System: CentOS release 5.4 (Final)
PHP Version: 5.3.8
Block user comment: N
Private report: N
New Comment:
Your interpretation was invalid. This is a common pitfall. The documentation is
very misleading, since it states that parenthenses are optional. This suggests
that they're a part of the language construct itself and work like parenthenses
in a function call. Unfortunely they aren't. They're interpreted as a part of
an expression that is later passed to `print` (`echo`, `include` and similar).
They have nothing to do with "function" itself. A nice example that shows this
issue is the following snippet:
print(string) TRUE;
I have posted a request (#60698) to change documentation.
Previous Comments:
------------------------------------------------------------------------
[2012-01-10 22:00:46] MarkAndrewSlade at gmail dot com
Oh, I see what happened. I agree with your recommendation. The documentation
says they are "not required" (implying optional), and they are used in the
actual example. I normally use echo, and without parens, so I just kinda
randomly came across this.
I'm not sure if you were saying the parser's interpretation was invalid or
mine,
but in case the latter and this is considered correct parsing, the
documentation
should be updated to reflect that it's "print <string>", without parens.
Developers can deduce for themselves that "print ('foo')" is allowed, but the
semantics will be clearer.
------------------------------------------------------------------------
[2012-01-10 10:24:08] phpmpan at mpan dot pl
Invalid interpretation of the code caused by misleading parenthenses.
1. false && print ('')
-> false && (print (''))
-> false && 1
-> false
2. print('') && false
-> (print (('') && false))
-> (print false)
-> 1
-> true
3. print('') && false && false
-> (print ((('') && false) && false))
-> (print false)
-> 1
-> true
4. (print('') && false) && true
-> ( print (('') && false) ) && true
-> (print false) && true
-> 1 && true
-> true
5. (print('') && false) && false
-> (print (('') && false) && false
-> (print false) && false
-> 1 && false
-> false
I believe that documentation for all language constructs (`echo`, `include`,
`print`, ...) should explicitly discourage use of parenthenses around
arguments. They're very misleading.
------------------------------------------------------------------------
[2012-01-10 02:26:21] MarkAndrewSlade at gmail dot com
Description:
------------
Unlike echo, the print construct is allowed inside logic clauses. If it is
reached (not short-circuited), it will cause the rest of that clause to be
true.
Tested with 5.3.8 and PHP 5.3.9RC5-dev, both with default configure.
Test script:
---------------
<?php
echo (false && print('')) ? "Fail\n" : "Pass\n";
echo (print('') && false) ? "Fail\n" : "Pass\n";
echo (print('') && false && false) ? "Fail\n" : "Pass\n";
echo ((print('') && false) && true) ? "Fail\n" : "Pass\n";
echo ((print('') && false) && false) ? "Fail\n" : "Pass\n";
?>
Expected result:
----------------
The word "Pass" five times.
Actual result:
--------------
The middle three fail. The first and last pass, and are included to
demonstrate
the limits of the bug.
------------------------------------------------------------------------
--
Edit this bug report at https://bugs.php.net/bug.php?id=60694&edit=1
