Doc #62590 [NEW]: usort & al : documentation about callback is wrong

From: fabien dot delorme at gmail dot com Operating system: MacOS lion PHP version: 5.3.14 Package: Documentation problem Bug Type: Documentation Problem Bug description:usort & al : documentation about callback is wrong Description: ------------ The documentation for usort function (and, it seems, other relative functions, although I haven't tested all of them) is slightly wrong regarding the callback function. It says : "The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second." However it sometimes results in wrong results if the return value is not precisely -1, 0 or 1. For example, returning $arg2 - $arg1 won't always perform the correct operation. Even if PHP builtin comparison functions all have this behavior (returning precisely -1, 0 or 1), this is not necessarily the case for user-defined functions and either code or documentation should be clear about what values shall be returned. Test script: --------------- $a=array(15.44, 5.76, 10.43, 6.12, 6.17, 7.21, 8.62, 8.91); usort($a, function($x, $y) {return $y - $x; }); var_dump($a); // The above would work if the lambda was something like // function($x, $y) { return $x == $y ? 0 : ($x < $y ? -1 : 1);} Expected result: ---------------- array(8) { [0]=> float(15.44) [1]=> float(10.43) [2]=> float(8.91) [3]=> float(8.62) [4]=> float(7.21) [5]=> float(6.17) [6]=> float(6.12) [7]=> float(5.76) } Actual result: -------------- array(8) { [0]=> float(15.44) [1]=> float(10.43) [2]=> float(8.62) [3]=> float(8.91) [4]=> float(7.21) [5]=> float(6.12) [6]=> float(5.76) [7]=> float(6.17) } -- Edit bug report at https://bugs.php.net/bug.php?id=62590&edit=1 -- Try a snapshot (PHP 5.4): https://bugs.php.net/fix.php?id=62590&r=trysnapshot54 Try a snapshot (PHP 5.3): https://bugs.php.net/fix.php?id=62590&r=trysnapshot53 Try a snapshot (trunk): https://bugs.php.net/fix.php?id=62590&r=trysnapshottrunk Fixed in SVN: https://bugs.php.net/fix.php?id=62590&r=fixed Fixed in SVN and need be documented: https://bugs.php.net/fix.php?id=62590&r=needdocs Fixed in release: https://bugs.php.net/fix.php?id=62590&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=62590&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=62590&r=needscript Try newer version: https://bugs.php.net/fix.php?id=62590&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=62590&r=support Expected behavior: https://bugs.php.net/fix.php?id=62590&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=62590&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=62590&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=62590&r=globals PHP 4 support discontinued: https://bugs.php.net/fix.php?id=62590&r=php4 Daylight Savings: https://bugs.php.net/fix.php?id=62590&r=dst IIS Stability: https://bugs.php.net/fix.php?id=62590&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=62590&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=62590&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=62590&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=62590&r=mysqlcfg