Bug #64324 [Nab]: Why 0 == 'BOOK' ?

Edit report at https://bugs.php.net/bug.php?id=64324&edit=1 ID: 64324 User updated by: dosergio at ig dot com dot br Reported by: dosergio at ig dot com dot br Summary: Why 0 == 'BOOK' ? Status: Not a bug Type: Bug Package: *General Issues Operating System: all PHP Version: Irrelevant Block user comment: N Private report: N New Comment: A good rule to be implemented by PHP is: If a comparison of simple equality ( == ) or simple inequality ( != ) is done between two different data types, PHP should cast both to boolean before comparing. Because 'TEXT' casts to true, 0 casts to false so 0 != 'TEXT' makes more sense than 0 == 'TEXT'. Previous Comments: ------------------------------------------------------------------------ [2013-02-28 19:12:25] dosergio at ig dot com dot br OK, you are right. That was the explanation I wanted: it depends on the type you compare. if( false == 'TEST') works correctly. Now it makes a little more sense to me. But javascript is still superior because inside a if() I suspect that any language should try to cast both to boolean. ------------------------------------------------------------------------ [2013-02-28 19:04:24] rasmus@php.net We don't want a special case for 0. By your logic 12 == 'TEST' should be true. You are assuming a cast to boolean even though neither side of the comparison is a boolean. Note that true == 'TEST' will match because here we cast to boolean. But 'TEST' cast to an integer is going to give you 0. ------------------------------------------------------------------------ [2013-02-28 18:58:51] dosergio at ig dot com dot br Conclusion: The exact analysis above done in javascript says I am right. I have no doubt that javascript makes more use of logic that php. ------------------------------------------------------------------------ [2013-02-28 18:51:56] dosergio at ig dot com dot br I know the use of ===. The supposed 'bug' that I think exists, is comparing 0 to a non-empty String with double == My concern is because: Observation 1: null, 0, "0", and "" all result as FALSE. Observation 2: BUT... "A STRING" evaluates as TRUE. SO... 0 == "" makes sense BUT... 0 == "A NON-EMPTY STRING" makes no sense. IMHO False would be the right answer. Take a little time to examine this: if( 0 ) echo "0 works as TRUE<br>"; else echo "0 works as false <br>"; if( "TEST") echo "'TEST' works as TRUE<br>"; else echo "'TEST' works as false <br>"; if( 0 == 'TEST') echo "But 0 == 'TEST' belies the statements above!"; ------------------------------------------------------------------------ [2013-02-28 15:22:59] rasmus@php.net You are doing a loose comparison between two different types. PHP has to pick a type for it. In this case it does 0 == (int)'TEST' and casting 'TEST' to an int is obviously going to give you 0. This is what you are going to want in most cases. eg. 12 == "12 " (with an extra space there). Chances are the "12 " came from user input since everything that comes from either the browser or your backend database comes to you as strings, you are going to want that comparison to work. If you cast both to strings instead they wouldn't. If you don't want PHP to guess, use === ------------------------------------------------------------------------ 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 https://bugs.php.net/bug.php?id=64324 -- Edit this bug report at https://bugs.php.net/bug.php?id=64324&edit=1