#50095 [NEW]: Unexpected behavior of precision of float numbers

From: majkl578 at gmail dot com Operating system: Linux Debian PHP version: 5.2.11 PHP Bug Type: Scripting Engine problem Bug description: Unexpected behavior of precision of float numbers Description: ------------ When dumping a float number, it is represented incorrectly. Generally, in some cases, PHP handles float numbers in invalid format. It is related to a setting of php.ini directive "precision". When a float number with one decimal place is dumped and high precision is set, it is not dumped in an original format, but in damaged one. Additional info: 32-bit system CPU: AMD Athlon64 Reproduce code: --------------- foreach (range(0, 30) as $precision) { ini_set('precision', $precision); echo $precision . ': '; var_dump(20.2); } Expected result: ---------------- 0: float(20) 1: float(20.2) 2: float(20.2) 3: float(20.2) 4: float(20.2) 5: float(20.2) 6: float(20.2) 7: float(20.2) 8: float(20.2) 9: float(20.2) 10: float(20.2) 11: float(20.2) 12: float(20.2) 13: float(20.2) 14: float(20.2) 15: float(20.2) 16: float(20.2) 17: float(20.2) 18: float(20.2) 19: float(20.2) 20: float(20.2) 21: float(20.2) 22: float(20.2) 23: float(20.2) 24: float(20.2) 25: float(20.2) 26: float(20.2) 27: float(20.2) 28: float(20.2) 29: float(20.2) 30: float(20.2) Actual result: -------------- 0: float(2.0E+1) 1: float(2.0E+1) 2: float(20) 3: float(20.2) 4: float(20.2) 5: float(20.2) 6: float(20.2) 7: float(20.2) 8: float(20.2) 9: float(20.2) 10: float(20.2) 11: float(20.2) 12: float(20.2) 13: float(20.2) 14: float(20.2) 15: float(20.2) 16: float(20.2) 17: float(20.199999999999999) 18: float(20.1999999999999993) 19: float(20.19999999999999929) 20: float(20.199999999999999289) 21: float(20.1999999999999992895) 22: float(20.19999999999999928946) 23: float(20.199999999999999289457) 24: float(20.1999999999999992894573) 25: float(20.19999999999999928945726) 26: float(20.199999999999999289457264) 27: float(20.1999999999999992894572642) 28: float(20.19999999999999928945726424) 29: float(20.19999999999999928945726424) 30: float(20.1999999999999992894572642399) -- Edit bug report at http://bugs.php.net/?id=50095&edit=1 -- Try a snapshot (PHP 5.2): http://bugs.php.net/fix.php?id=50095&r=trysnapshot52 Try a snapshot (PHP 5.3): http://bugs.php.net/fix.php?id=50095&r=trysnapshot53 Try a snapshot (PHP 6.0): http://bugs.php.net/fix.php?id=50095&r=trysnapshot60 Fixed in SVN: http://bugs.php.net/fix.php?id=50095&r=fixed Fixed in SVN and need be documented: http://bugs.php.net/fix.php?id=50095&r=needdocs Fixed in release: http://bugs.php.net/fix.php?id=50095&r=alreadyfixed Need backtrace: http://bugs.php.net/fix.php?id=50095&r=needtrace Need Reproduce Script: http://bugs.php.net/fix.php?id=50095&r=needscript Try newer version: http://bugs.php.net/fix.php?id=50095&r=oldversion Not developer issue: http://bugs.php.net/fix.php?id=50095&r=support Expected behavior: http://bugs.php.net/fix.php?id=50095&r=notwrong Not enough info: http://bugs.php.net/fix.php?id=50095&r=notenoughinfo Submitted twice: http://bugs.php.net/fix.php?id=50095&r=submittedtwice register_globals: http://bugs.php.net/fix.php?id=50095&r=globals PHP 4 support discontinued: http://bugs.php.net/fix.php?id=50095&r=php4 Daylight Savings: http://bugs.php.net/fix.php?id=50095&r=dst IIS Stability: http://bugs.php.net/fix.php?id=50095&r=isapi Install GNU Sed: http://bugs.php.net/fix.php?id=50095&r=gnused Floating point limitations: http://bugs.php.net/fix.php?id=50095&r=float No Zend Extensions: http://bugs.php.net/fix.php?id=50095&r=nozend MySQL Configuration Error: http://bugs.php.net/fix.php?id=50095&r=mysqlcfg