#29516 [NEW]: Mathematical calculations give unexpected result

From: beckwest22 at yahoo dot com Operating system: Windows XP PHP version: 5.0.0 PHP Bug Type: Math related Bug description: Mathematical calculations give unexpected result Description: ------------ I have been reading that doing some mathematical calculations with floats and integers in php gives some unexpected results. I am not sure if this is a bug or not. When I do a combination of division and subtraction with the number 19, I get unexpected results. I would appreciate any light you could shine on this subject. Modules compiled with PHP: I did not compile any modules with PHP. The only thing different in my php.ini file is that I uncommented the extension=php_mysql.dll line in the file. Reproduce code: --------------- <?php $num = 19; $res = $num/10; echo $res; echo "<br>"; $res1 = ($num%10)/10; echo $res1; echo "<br>"; $res2 = $res - $res1; echo $res2; $final_result = $res2 - 1; echo "<br>"; echo $final_result; ?> Expected result: ---------------- This is what I expect from the calculations: $res = 19/10; // equals 1.9 $res1 = (19%10)/10; // equals 0.9 $res2 = 1.9 - 0.9; // equals 1 $final_result = 1 - 1; // equals 0 expected $final_result to be 0 Actual result: -------------- $final_result equals -1.11022302463E-016 -- Edit bug report at http://bugs.php.net/?id=29516&edit=1 -- Try a CVS snapshot (php4): http://bugs.php.net/fix.php?id=29516&r=trysnapshot4 Try a CVS snapshot (php5): http://bugs.php.net/fix.php?id=29516&r=trysnapshot5 Fixed in CVS: http://bugs.php.net/fix.php?id=29516&r=fixedcvs Fixed in release: http://bugs.php.net/fix.php?id=29516&r=alreadyfixed Need backtrace: http://bugs.php.net/fix.php?id=29516&r=needtrace Need Reproduce Script: http://bugs.php.net/fix.php?id=29516&r=needscript Try newer version: http://bugs.php.net/fix.php?id=29516&r=oldversion Not developer issue: http://bugs.php.net/fix.php?id=29516&r=support Expected behavior: http://bugs.php.net/fix.php?id=29516&r=notwrong Not enough info: http://bugs.php.net/fix.php?id=29516&r=notenoughinfo Submitted twice: http://bugs.php.net/fix.php?id=29516&r=submittedtwice register_globals: http://bugs.php.net/fix.php?id=29516&r=globals PHP 3 support discontinued: http://bugs.php.net/fix.php?id=29516&r=php3 Daylight Savings: http://bugs.php.net/fix.php?id=29516&r=dst IIS Stability: http://bugs.php.net/fix.php?id=29516&r=isapi Install GNU Sed: http://bugs.php.net/fix.php?id=29516&r=gnused Floating point limitations: http://bugs.php.net/fix.php?id=29516&r=float