#32082 [NEW]: Comparing of floating point values fail

From: weber at mapsolute dot com Operating system: Linux PHP version: 4.3.9 PHP Bug Type: Math related Bug description: Comparing of floating point values fail Description: ------------ If you compare two equal floating point values for uneven the compare fails (it returns true) and I can see no reason why. I've checked the PHP manual (http://uk.php.net/manual/en/language.types.float.php), but this doesn't explain the behave. The two numbers below must be binary equal, independend if you save them as single or double precision floating point numbers and even if you would store them as double and convert into float for comparing, they must stay binary equal. Even as string they must be binary equal. Therefore comparing them should return true in any case. Quote from http://en.wikipedia.org/wiki/IEEE_754: Comparing floating-point numbers An interesting feature of this particular representation is that it makes comparisons of numbers of the same sign which are not NaNs simple. For positive numbers (the sign bit is 0) a and b, then a < b whenever the unsigned binary integers with the same bit patterns as a and b are also ordered the same way. In other words if you are comparing two positive floating-point numbers (known not to be NaNs) you can just use an unsigned binary integer comparison using the same bits. Reproduce code: --------------- <html><body><?php $a = 437.674240047; $b = 437.674240047; if( $a != $b ) echo "<p>OK</p>"; else echo "<p>WRONG</p>"; var_dump($a); echo "<br>"; var_dump($b); ?></body></html> Expected result: ---------------- OK float(437.674240047) float(437.674240047) Actual result: -------------- WRONG float(437.674240047) float(437.674240047) -- Edit bug report at http://bugs.php.net/?id=32082&edit=1 -- Try a CVS snapshot (php4): http://bugs.php.net/fix.php?id=32082&r=trysnapshot4 Try a CVS snapshot (php5.0): http://bugs.php.net/fix.php?id=32082&r=trysnapshot50 Try a CVS snapshot (php5.1): http://bugs.php.net/fix.php?id=32082&r=trysnapshot51 Fixed in CVS: http://bugs.php.net/fix.php?id=32082&r=fixedcvs Fixed in release: http://bugs.php.net/fix.php?id=32082&r=alreadyfixed Need backtrace: http://bugs.php.net/fix.php?id=32082&r=needtrace Need Reproduce Script: http://bugs.php.net/fix.php?id=32082&r=needscript Try newer version: http://bugs.php.net/fix.php?id=32082&r=oldversion Not developer issue: http://bugs.php.net/fix.php?id=32082&r=support Expected behavior: http://bugs.php.net/fix.php?id=32082&r=notwrong Not enough info: http://bugs.php.net/fix.php?id=32082&r=notenoughinfo Submitted twice: http://bugs.php.net/fix.php?id=32082&r=submittedtwice register_globals: http://bugs.php.net/fix.php?id=32082&r=globals PHP 3 support discontinued: http://bugs.php.net/fix.php?id=32082&r=php3 Daylight Savings: http://bugs.php.net/fix.php?id=32082&r=dst IIS Stability: http://bugs.php.net/fix.php?id=32082&r=isapi Install GNU Sed: http://bugs.php.net/fix.php?id=32082&r=gnused Floating point limitations: http://bugs.php.net/fix.php?id=32082&r=float No Zend Extensions: http://bugs.php.net/fix.php?id=32082&r=nozend MySQL Configuration Error: http://bugs.php.net/fix.php?id=32082&r=mysqlcfg