note 109663 added to language.operators.arithmetic

Certain functions eg. crc32() can return an integer value outside the range of precision handled by an integer arithmetic operator. Making the assumption that any operator has arbitrary precision is not portable. I created a sample code here and ran it off a random virtual server. Do note the output may vary according to your environment but it is sufficient to illustrate the possible gotchas. <?php $checksum = crc32("The quick brown fox jumped over the lazy dog."); $divisor = 256; $a = $checksum; echo "Original crc32 output a = $a, to divide by $divisor\n"; $r = $a % $divisor; echo "% operator: r = $r \n"; $r = intval(fmod($a, $divisor)); echo "fmod function: r = $r \n"; $r = bcmod($a, $divisor); echo "bcmod function: r = $r \n"; echo "\n"; $a = sprintf("%u", $checksum); echo "sprintf crc32 output a = $a, to divide by $divisor\n"; $r = $a % $divisor; echo "% operator: r = $r \n"; $r = intval(fmod($a, $divisor)); echo "fmod function: r = $r \n"; $r = bcmod($a, $divisor); echo "bcmod function: r = $r \n"; ?> Output: Original crc32 output a = -2103228862, to divide by 256 % operator: r = -190 fmod function: r = -190 bcmod function: r = -190 sprintf crc32 output a = 2191738434, to divide by 256 % operator: r = 255 fmod function: r = 66 bcmod function: r = 66 Conclusion: Note that integer arithmetic operators do not have the precision to work correctly in some applications. ---- Server IP: 69.147.83.197 Probable Submitter: 220.255.2.131 ---- Manual Page -- http://www.php.net/manual/en/language.operators.arithmetic.php Edit -- https://master.php.net/note/edit/109663 Del: integrated -- https://master.php.net/note/delete/109663/integrated Del: useless -- https://master.php.net/note/delete/109663/useless Del: bad code -- https://master.php.net/note/delete/109663/bad+code Del: spam -- https://master.php.net/note/delete/109663/spam Del: non-english -- https://master.php.net/note/delete/109663/non-english Del: in docs -- https://master.php.net/note/delete/109663/in+docs Del: other reasons-- https://master.php.net/note/delete/109663 Reject -- https://master.php.net/note/reject/109663 Search -- https://master.php.net/manage/user-notes.php