note 124871 added to math.constants

Caution when using variables with the value NAN (or directly NAN, which would not be logical) if the value is converted in any form (integer, string or other non-float format)! In that case, NAN is converted to 0. (e.g. as an index in an array, argument of a method that takes it as a non-float parameter, etc.). This bug has been reported several times, but is still present in the current version PHP 7.3.15. Example 1: $array = [0 => 'zero', 1 => 'one', 2 => 'two']; $index = NAN; echo $array[$index]; // echo 'zero' and not as axcepted throws an exception or at least a warning 'undefined offset NAN ...' Example 2: function f((int) $p) { return $p; } echo f(NAN); // echo 0 because the argument (NAN) has been converted to integer (0) It would have to be checked in both cases explicitly for is_nan(): 1: if(is_nan($index)){ <throw Exception> }else{ echo $array[$index]; }; 2: function f($p){ // without converting!!! if(is_nan($p)){ <throw Exception> }else{ return (int)$p; // actually a correct conversion to Integer would have to be checked because the parser does not check this here. }; } ---- Server IP: 45.112.84.4 Probable Submitter: 103.51.167.36 (proxied: 185.9.19.119) ---- Manual Page -- http://php.net/manual/en/math.constants.php Edit -- https://master.php.net/note/edit/124871 Del: integrated -- https://master.php.net/note/delete/124871/integrated Del: useless -- https://master.php.net/note/delete/124871/useless Del: bad code -- https://master.php.net/note/delete/124871/bad+code Del: spam -- https://master.php.net/note/delete/124871/spam Del: non-english -- https://master.php.net/note/delete/124871/non-english Del: in docs -- https://master.php.net/note/delete/124871/in+docs Del: other reasons-- https://master.php.net/note/delete/124871 Reject -- https://master.php.net/note/reject/124871 Search -- https://master.php.net/manage/user-notes.php