Bug #66450 [NEW]: Casting extremely large E notation strings to floats results in incorrect value

From: howard at zedcore dot com Operating system: Debian Gnu/Linux "Wheezy" 7.2 PHP version: Irrelevant Package: *Programming Data Structures Bug Type: Bug Bug description:Casting extremely large E notation strings to floats results in incorrect value Description: ------------ Casting a very large float into a string and back-again results in a different value. The string representation of both values from var_dump() is the same, and as expected. Reproducible on PHP 5.4.4 and PHP 5.3.10 (Not able to upgrade to the latest PHP release at work but I'll try to reproduce at home soon). Test script: --------------- var_dump(exp(100), (string)exp(100), exp(100) == (string)exp(100), exp(100) - (string)exp(100)); Expected result: ---------------- float(2.6881171418161E+43) float(2.6881171418161E+43) bool(true) float(0) Actual result: -------------- float(2.6881171418161E+43) float(2.6881171418161E+43) bool(false) float(3.5652673131419E+29) -- Edit bug report at https://bugs.php.net/bug.php?id=66450&edit=1 -- Try a snapshot (PHP 5.4): https://bugs.php.net/fix.php?id=66450&r=trysnapshot54 Try a snapshot (PHP 5.5): https://bugs.php.net/fix.php?id=66450&r=trysnapshot55 Try a snapshot (trunk): https://bugs.php.net/fix.php?id=66450&r=trysnapshottrunk Fixed in SVN: https://bugs.php.net/fix.php?id=66450&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=66450&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=66450&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=66450&r=needscript Try newer version: https://bugs.php.net/fix.php?id=66450&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=66450&r=support Expected behavior: https://bugs.php.net/fix.php?id=66450&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=66450&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=66450&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=66450&r=globals PHP 4 support discontinued: https://bugs.php.net/fix.php?id=66450&r=php4 Daylight Savings: https://bugs.php.net/fix.php?id=66450&r=dst IIS Stability: https://bugs.php.net/fix.php?id=66450&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=66450&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=66450&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=66450&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=66450&r=mysqlcfg