ID: 36799 User updated by: cleo at anarki dot dk Reported By: cleo at anarki dot dk Status: Bogus Bug Type: *General Issues Operating System: WinXP, Mandriva Linux 2006 PHP Version: 5.1.2 New Comment:
Thanks Rasmus, At last someone comes up with an explanation. I can see the point of having to versions of boolean and, each with different precedence. However, the precedence of 'and' should definitely not be lower than '='. What is your argument? I mean: $test= true and false; echo $test ? "ok" : "nope"; I am sorry, but it can never be correct to let $test evaluate to true here!!! As I see it, PHP does the following: ($test= true) and false So, $test will be set to true, and the assignment will be true, and that assignment will be and'ed with false, and the result is discarded. But who would want that? Conclusion: $test1= true and false; // Evaluates to true $test2= true && false; // Evaluates to false '=' and 'and' have wrong precedences in PHP. One should always use && instead of 'and', as && used in an assignment statement gives the results you would expect from boolean algebra. And 'and' does not. Best regards, and the hope of recognition of my arguments Claus Holm, Copenhagen, Denmark. Previous Comments: ------------------------------------------------------------------------ [2006-03-21 01:59:51] [EMAIL PROTECTED] The whole point of 'and','or' is to be the low-precedence version of '&&', '||'. If you want high-precedence, use &&. ------------------------------------------------------------------------ [2006-03-20 20:05:03] [EMAIL PROTECTED] http://www.php.net/manual/en/language.operators.php#language.operators.precedence ------------------------------------------------------------------------ [2006-03-20 19:59:05] cleo at anarki dot dk All right, ( (p1) and (p2) ) evaluates correctly, but that doesn't change the fact, that (p1) and (p2) evaluates totally wrongly. And I don't see the difference. Neither from a mathematician's nor a computer scientist's point of view. Therefore, I still strongly argue, that this is a bug in PHP's way of evaluating boolean expressions. Best regards Claus Holm from Copenhagen ------------------------------------------------------------------------ [2006-03-20 18:09:23] [EMAIL PROTECTED] $h = 25; $res = (($h>=0) and ($h<=23)); ------------------------------------------------------------------------ [2006-03-20 17:47:15] cleo at anarki dot dk Description: ------------ Consider the following piece of code: $res= ($h>=0) and ($h<=23); It could be used to determine if a user has submitted an hour between 0 and 23. However, if the user enters 25, then the function evaluates to true!!!! If you reverse the order of the operands like this: $res = ($h<=23) and ($h>=0); ...then a $h value of 25 will make the function evaluate to false. But now -1 will make it evaluate to true! So clearly, this must be a major bug. Best regards Claus Holm, Copenhagen, Denmark Reproduce code: --------------- <? if (isset($_POST['test'])) { $hours= $_POST['e_hours']; $hours= (integer)$hours; echo "You entered $hours <br>"; echo 'Now we test: ($hours>=0) and ($hours<=23)<br>'; $test1= ($hours>=0) and ($hours<=23); echo $test1 ? "ok" : "nope"; echo "<br>"; echo 'And now we test: ($hours<=23)and($hours>=0)<br>'; $test2= ($hours<=23) and ($hours>=0); echo $test2 ? "ok" : "nope"; } else { ?> Input an hour between 0 and 23:<br> <FORM action="<?=$_SERVER['PHP_SELF']?>" method="post"> <INPUT type="text" name="e_hours" value=""><br> <INPUT type="submit" name="test" value="Run test"> </form> <?} ?> Expected result: ---------------- If the value 25 is entered, then I should see this: You entered 25 Now we test: ($hours>=0) and ($hours<=23) nope And now we test: ($hours<=23) and ($hours>=0) nope Actual result: -------------- You entered 25 Now we test: ($hours>=0) and ($hours<=23) ok And now we test: ($hours<=23) and ($hours>=0) nope ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/?id=36799&edit=1
