#39579 [Bgs]: Comparing zero & string values in boolean comparison has unexpected behaviour

ID: 39579 Updated by: mgf@php.net Reported By: iain at workingsoftware dot com dot au Status: Bogus Bug Type: Variables related Operating System: FreeBSD 6.1 PHP Version: 5.2.0 New Comment: It's not a problem -- it's a feature, and it's documented at the address I've just quoted, which describes evaluation of a string in any numeric context. Previous Comments: ------------------------------------------------------------------------ [2006-11-22 11:14:47] iain at workingsoftware dot com dot au it's not the behaviour of how a string is cast to an integer that i'm talking about, but if i have a comparison: if($value == Class::CONSTANT) and the class constant is a string, it's not immediately apparent that if $value == 0 then this will evaluate to true. maybe warning is too strong, but a notice might be good in the event that a non-strict == operation returns true because one of the operands is 0 and the other operand is a value that evaluates to 0 when cast as an int. anyway, i guess if php has been around for this long without anyone mentioning it yet ... i mean, this is the first time i've come across the problem. if a notice had been emitted it would have been a time saver. ------------------------------------------------------------------------ [2006-11-22 11:06:57] mgf@php.net And, besides, this behaviour is documented at http://www.php.net/manual/en/language.types.string.php#language.types.string.conversion ------------------------------------------------------------------------ [2006-11-22 09:39:26] johannes@php.net Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.php.net/manual/ and the instructions on how to report a bug at http://bugs.php.net/how-to-report.php That's how PHP works and it won't change. ------------------------------------------------------------------------ [2006-11-22 08:35:22] iain at workingsoftware dot com dot au well it seems to me that at least a warning should be given when comparing an integer 0 to a non-integer value that evaluates to 0 when cast as an int unless an explicit type cast is used without using strict equals. i can see why this behaviour is not a bug, because (int)'SOME STRING' == 0, but it's also has the potential to cause unexpected results/bugs unless you use strict equals everywhere. in this case, i fixed the problem by using === instead of ==, but it took a bit of time to track down the error because there was no warning or anything. i think that it would be better to require someone to do: if($value == (int)'SOME STRING') OR if($value === 'SOME STRING') in order to avoid a warning being emmited if $value == 0. ------------------------------------------------------------------------ [2006-11-22 08:17:01] derick@php.net Thank you for taking the time to write to us, but this is not a bug. Please double-check the documentation available at http://www.php.net/manual/ and the instructions on how to report a bug at http://bugs.php.net/how-to-report.php . ------------------------------------------------------------------------ The remainder of the comments for this report are too long. To view the rest of the comments, please view the bug report online at http://bugs.php.net/39579 -- Edit this bug report at http://bugs.php.net/?id=39579&edit=1