Bug #53104 [Ana->Nab]: min() and max() treat NULL and BOOL differently

Edit report at https://bugs.php.net/bug.php?id=53104&edit=1 ID: 53104 Updated by: yohgaki@php.net Reported by: frase at cs dot wisc dot edu Summary: min() and max() treat NULL and BOOL differently -Status: Analyzed +Status: Not a bug Type: Bug Package: Scripting Engine problem Operating System: any PHP Version: any Block user comment: N Private report: N New Comment: Apparently, I also misunderstood that BOOL/NULL evaluated as INT, but it's evaluated as BOOL. Therefore, this is not a bug. NULL or FALSE < (-1000) is evaluated as (both operands are converted to bool) FALSE < (bool)(-1000) and (FALSE < TRUE) is FALSE Previous Comments: ------------------------------------------------------------------------ [2013-10-23 08:23:29] yohgaki@php.net I forgot to edit values. So BOOL works some what but it does not compared as operators. [yohgaki@dev php-5.5]$ php -r "var_dump(min([2, 3, false]));" bool(false) [yohgaki@dev php-5.5]$ php -r "var_dump(min([-2, -3, false]));" bool(false) [yohgaki@dev php-5.5]$ php -r "var_dump(-3 < false);" bool(false) [yohgaki@dev php-5.5]$ php -r "var_dump(min([2, 3, true]));" int(2) [yohgaki@dev php-5.5]$ php -r "var_dump(max([2, 3, true]));" int(3) [yohgaki@dev php-5.5]$ php -r "var_dump(max(-2, -3, true));" int(-2) It seems "false" is evaluated as the smallest and "true" is ignored. We have serious mess here. Since min()/max() supports array type, we cannot convert NULL/BOOL parameter to INT as it would returns different results for array parameter. For the same reason, black listing NULL/BOOL parameters do not work. Anyone has clever idea? Corrected test code ------------- <?php echo "min(-1,null) = "; var_dump(min(-1,null)); echo "\n"; /* NULL */ echo "min( 1,null) = "; var_dump(min( 1,null)); echo "\n"; /* NULL */ echo "max(-1,null) = "; var_dump(max(-1,null)); echo "\n"; /* int(-1) */ echo "max( 1,null) = "; var_dump(max( 1,null)); echo "\n"; /* int(1) */ echo "min(-1,false) = "; var_dump(min(-1,null)); echo "\n"; /* NULL */ echo "min( 1,false) = "; var_dump(min( 1,null)); echo "\n"; /* NULL */ echo "max(-1,false) = "; var_dump(max(-1,null)); echo "\n"; /* int(-1) */ echo "max( 1,false) = "; var_dump(max( 1,null)); echo "\n"; /* int(1) */ echo "min(-1,true) = "; var_dump(min(-1,null)); echo "\n"; /* NULL */ echo "min( 1,true) = "; var_dump(min( 1,null)); echo "\n"; /* NULL */ echo "max(-1,true) = "; var_dump(max(-1,null)); echo "\n"; /* int(-1) */ echo "max( 1,true) = "; var_dump(max( 1,null)); echo "\n"; /* int(1) */ echo "min(null,-1) = "; var_dump(min(null,-1)); echo "\n"; /* NULL */ echo "min(null, 1) = "; var_dump(min(null, 1)); echo "\n"; /* NULL */ echo "max(null,-1) = "; var_dump(max(null,-1)); echo "\n"; /* int(-1) */ echo "max(null, 1) = "; var_dump(max(null, 1)); echo "\n"; /* int(1) */ echo "min(false,-1) = "; var_dump(min(null,-1)); echo "\n"; /* NULL */ echo "min(false, 1) = "; var_dump(min(null, 1)); echo "\n"; /* NULL */ echo "max(false,-1) = "; var_dump(max(null,-1)); echo "\n"; /* int(-1) */ echo "max(false, 1) = "; var_dump(max(null, 1)); echo "\n"; /* int(1) */ echo "min(true,-1) = "; var_dump(min(null,-1)); echo "\n"; /* NULL */ echo "min(true, 1) = "; var_dump(min(null, 1)); echo "\n"; /* NULL */ echo "max(true,-1) = "; var_dump(max(null,-1)); echo "\n"; /* int(-1) */ echo "max(true, 1) = "; var_dump(max(null, 1)); echo "\n"; /* int(1) */ echo "min(10,-1,null) = "; var_dump(min(10,-1,null)); echo "\n"; /* NULL */ echo "min(10, 1,null) = "; var_dump(min(10, 1,null)); echo "\n"; /* NULL */ echo "max(10,-1,null) = "; var_dump(max(10,-1,null)); echo "\n"; /* int(10) */ echo "max(10, 1,null) = "; var_dump(max(10, 1,null)); echo "\n"; /* int(10) */ echo "min(10,-1,false) = "; var_dump(min(10,-1,false)); echo "\n"; /* false */ echo "min(10, 1,false) = "; var_dump(min(10, 1,false)); echo "\n"; /* false */ echo "max(10,-1,false) = "; var_dump(max(10,-1,false)); echo "\n"; /* int(10) */ echo "max(10, 1,false) = "; var_dump(max(10, 1,false)); echo "\n"; /* int(10) */ echo "min(10,-1,true) = "; var_dump(min(10,-1,true)); echo "\n"; /* -1 */ echo "min(10, 1,true) = "; var_dump(min(10, 1,true)); echo "\n"; /* 1 */ echo "max(10,-1,true) = "; var_dump(max(10,-1,true)); echo "\n"; /* int(10) */ echo "max(10, 1,true) = "; var_dump(max(10, 1,true)); echo "\n"; /* int(10) */ echo "min([10,-1,null]) = "; var_dump([min(10,-1,null)]); echo "\n"; /* [NULL] */ echo "min([10, 1,null]) = "; var_dump([min(10, 1,null)]); echo "\n"; /* [NULL] */ echo "max([10,-1,null]) = "; var_dump([max(10,-1,null)]); echo "\n"; /* [int(10)] */ echo "max([10, 1,null]) = "; var_dump([max(10, 1,null)]); echo "\n"; /* [int(10)] */ echo "min([10,-1,false]) = "; var_dump([min(10,-1,null)]); echo "\n"; /* [NULL] */ echo "min([10, 1,false]) = "; var_dump([min(10, 1,null)]); echo "\n"; /* [NULL] */ echo "max([10,-1,false]) = "; var_dump([max(10,-1,null)]); echo "\n"; /* [int(10)] */ echo "max([10, 1,false]) = "; var_dump([max(10, 1,null)]); echo "\n"; /* [int(10)] */ echo "min([10,-1,true]) = "; var_dump([min(10,-1,null)]); echo "\n"; /* [NULL] */ echo "min([10, 1,true]) = "; var_dump([min(10, 1,null)]); echo "\n"; /* [NULL] */ echo "max([10,-1,true]) = "; var_dump([max(10,-1,null)]); echo "\n"; /* [int(10)] */ echo "max([10, 1,true]) = "; var_dump([max(10, 1,null)]); echo "\n"; /* [int(10)] */ ------------------------------------------------------------------------ [2013-10-23 07:46:49] yohgaki@php.net The comparison is done by compare_function() in zend_operators.c Not only NULL, but also BOOL type also has the same problem. I haven't check fully for ARRAY, but it seems NULL and BOOL break comparison. We have inconsistency with comparison operators. $ php -r "var_dump(-1 > NULL);" bool(true) $ php -r "var_dump(-1 < NULL);" bool(false) $ php -r "var_dump(min(-1,NULL));" NULL $ php -r "var_dump(min(NULL, -1));" NULL Comparison operators evaluate comparison as PHP users expect, but min() does not. This behavior is not intuitive. We may fix this issue or document this unexpected behavior in min() manual. (+ other functions if there are affected) I think this is better to be fixed even if there is BC issue at some point. Any comments? Test code ----------------------------- <?php echo "min(-1,null) = "; var_dump(min(-1,null)); echo "\n"; /* NULL */ echo "min( 1,null) = "; var_dump(min( 1,null)); echo "\n"; /* NULL */ echo "max(-1,null) = "; var_dump(max(-1,null)); echo "\n"; /* int(-1) */ echo "max( 1,null) = "; var_dump(max( 1,null)); echo "\n"; /* int(1) */ echo "min(-1,false) = "; var_dump(min(-1,null)); echo "\n"; /* NULL */ echo "min( 1,false) = "; var_dump(min( 1,null)); echo "\n"; /* NULL */ echo "max(-1,false) = "; var_dump(max(-1,null)); echo "\n"; /* int(-1) */ echo "max( 1,false) = "; var_dump(max( 1,null)); echo "\n"; /* int(1) */ echo "min(-1,true) = "; var_dump(min(-1,null)); echo "\n"; /* NULL */ echo "min( 1,true) = "; var_dump(min( 1,null)); echo "\n"; /* NULL */ echo "max(-1,true) = "; var_dump(max(-1,null)); echo "\n"; /* int(-1) */ echo "max( 1,true) = "; var_dump(max( 1,null)); echo "\n"; /* int(1) */ echo "min(null,-1) = "; var_dump(min(null,-1)); echo "\n"; /* NULL */ echo "min(null, 1) = "; var_dump(min(null, 1)); echo "\n"; /* NULL */ echo "max(null,-1) = "; var_dump(max(null,-1)); echo "\n"; /* int(-1) */ echo "max(null, 1) = "; var_dump(max(null, 1)); echo "\n"; /* int(1) */ echo "min(false,-1) = "; var_dump(min(null,-1)); echo "\n"; /* NULL */ echo "min(false, 1) = "; var_dump(min(null, 1)); echo "\n"; /* NULL */ echo "max(false,-1) = "; var_dump(max(null,-1)); echo "\n"; /* int(-1) */ echo "max(false, 1) = "; var_dump(max(null, 1)); echo "\n"; /* int(1) */ echo "min(true,-1) = "; var_dump(min(null,-1)); echo "\n"; /* NULL */ echo "min(true, 1) = "; var_dump(min(null, 1)); echo "\n"; /* NULL */ echo "max(true,-1) = "; var_dump(max(null,-1)); echo "\n"; /* int(-1) */ echo "max(true, 1) = "; var_dump(max(null, 1)); echo "\n"; /* int(1) */ echo "min(10,-1,null) = "; var_dump(min(10,-1,null)); echo "\n"; /* NULL */ echo "min(10, 1,null) = "; var_dump(min(10, 1,null)); echo "\n"; /* NULL */ echo "max(10,-1,null) = "; var_dump(max(10,-1,null)); echo "\n"; /* int(10) */ echo "max(10, 1,null) = "; var_dump(max(10, 1,null)); echo "\n"; /* int(10) */ echo "min(10,-1,false) = "; var_dump(min(10,-1,null)); echo "\n"; /* NULL */ echo "min(10, 1,false) = "; var_dump(min(10, 1,null)); echo "\n"; /* NULL */ echo "max(10,-1,false) = "; var_dump(max(10,-1,null)); echo "\n"; /* int(10) */ echo "max(10, 1,false) = "; var_dump(max(10, 1,null)); echo "\n"; /* int(10) */ echo "min(10,-1,true) = "; var_dump(min(10,-1,null)); echo "\n"; /* NULL */ echo "min(10, 1,true) = "; var_dump(min(10, 1,null)); echo "\n"; /* NULL */ echo "max(10,-1,true) = "; var_dump(max(10,-1,null)); echo "\n"; /* int(10) */ echo "max(10, 1,true) = "; var_dump(max(10, 1,null)); echo "\n"; /* int(10) */ echo "min([10,-1,null]) = "; var_dump([min(10,-1,null)]); echo "\n"; /* [NULL] */ echo "min([10, 1,null]) = "; var_dump([min(10, 1,null)]); echo "\n"; /* [NULL] */ echo "max([10,-1,null]) = "; var_dump([max(10,-1,null)]); echo "\n"; /* [int(10)] */ echo "max([10, 1,null]) = "; var_dump([max(10, 1,null)]); echo "\n"; /* [int(10)] */ echo "min([10,-1,false]) = "; var_dump([min(10,-1,null)]); echo "\n"; /* [NULL] */ echo "min([10, 1,false]) = "; var_dump([min(10, 1,null)]); echo "\n"; /* [NULL] */ echo "max([10,-1,false]) = "; var_dump([max(10,-1,null)]); echo "\n"; /* [int(10)] */ echo "max([10, 1,false]) = "; var_dump([max(10, 1,null)]); echo "\n"; /* [int(10)] */ echo "min([10,-1,true]) = "; var_dump([min(10,-1,null)]); echo "\n"; /* [NULL] */ echo "min([10, 1,true]) = "; var_dump([min(10, 1,null)]); echo "\n"; /* [NULL] */ echo "max([10,-1,true]) = "; var_dump([max(10,-1,null)]); echo "\n"; /* [int(10)] */ echo "max([10, 1,true]) = "; var_dump([max(10, 1,null)]); echo "\n"; /* [int(10)] */ ------------------- ------------------------------------------------------------------------ [2012-04-26 20:52:28] roeitell at gmail dot com Actually changing behavior might cause serious bc issues for some users possibly relying on this; but attached is a patch which generates E_WARNING for min/max receiving a NULL parameter. ------------------------------------------------------------------------ [2010-10-19 19:39:43] frase at cs dot wisc dot edu Description: ------------ The min() and max() functions treat null values as "negative infinity", which is not documented or (to me) particularly intuitive. I would expect null to either be treated as 0 (as "(int)null" does), or ignore it entirely (which min() does not, but max() does by virtue of any value being greater than negative infinity). Test script: --------------- echo "min(-1,null) = "; var_dump(min(-1,null)); echo "\n"; /* NULL */ echo "min( 1,null) = "; var_dump(min( 1,null)); echo "\n"; /* NULL */ echo "max(-1,null) = "; var_dump(max(-1,null)); echo "\n"; /* int(-1) */ echo "max( 1,null) = "; var_dump(max( 1,null)); echo "\n"; /* int(1) */ Expected result: ---------------- min(-1,null) = int(-1) min( 1,null) = int(1 or 0) max(-1,null) = int(-1 or 0) max( 1,null) = int(1) Actual result: -------------- min(-1,null) = NULL min( 1,null) = NULL max(-1,null) = int(-1) max( 1,null) = int(1) ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=53104&edit=1