Bug #70754 [NEW]: array_udiff compares the same values multiple times

From: php_bugs at multiwebinc dot com Operating system: PHP version: 7.0.0RC5 Package: Performance problem Bug Type: Bug Bug description:array_udiff compares the same values multiple times Description: ------------ All versions of PHP seem to be inefficient at executing array_udiff. The values in $a in the callback function are all compared twice. If the callback function is expensive, this would affect performance. Also, some comparisons are unnecessary. Test script: --------------- /* Note: The callback function just returns 0 every time, which means that all values in both arrays are considered equal. */ function callback($a, $b) { echo "\$a = $a; \$b= $b; "; echo "<br>\n"; return 0; } $array1 = array("first_0", "first_1", "first_2", "first_3", "first_4" ); $array2 = array("second_0", "second_1", "second_2", "second_3", "second_4"); $result = array_udiff($array1, $array2, "callback"); Actual result: -------------- $a = first_2; $b= first_1; $a = first_4; $b= first_2; $a = first_2; $b= first_0; $a = first_3; $b= first_2; $a = first_4; $b= first_3; // Unnecessary since we already know these are equal $a = first_1; $b= first_0; // Unnecessary since we already know these are equal $a = second_2; $b= second_1; $a = second_4; $b= second_2; $a = second_2; $b= second_0; $a = second_3; $b= second_2; $a = second_4; $b= second_3; // Unnecessary since we already know these are equal $a = second_1; $b= second_0; // Unnecessary since we already know these are equal $a = first_4; $b= second_4; $a = first_4; $b= first_3; // Duplicate. Already tested above. $a = first_3; $b= first_2; // Duplicate. Already tested above. $a = first_2; $b= first_1; // Duplicate. Already tested above. $a = first_1; $b= first_0; // Duplicate. Already tested above. -- Edit bug report at https://bugs.php.net/bug.php?id=70754&edit=1 -- Try a snapshot (PHP 5.4): https://bugs.php.net/fix.php?id=70754&r=trysnapshot54 Try a snapshot (PHP 5.5): https://bugs.php.net/fix.php?id=70754&r=trysnapshot55 Try a snapshot (trunk): https://bugs.php.net/fix.php?id=70754&r=trysnapshottrunk Fixed in SVN: https://bugs.php.net/fix.php?id=70754&r=fixed Fixed in release: https://bugs.php.net/fix.php?id=70754&r=alreadyfixed Need backtrace: https://bugs.php.net/fix.php?id=70754&r=needtrace Need Reproduce Script: https://bugs.php.net/fix.php?id=70754&r=needscript Try newer version: https://bugs.php.net/fix.php?id=70754&r=oldversion Not developer issue: https://bugs.php.net/fix.php?id=70754&r=support Expected behavior: https://bugs.php.net/fix.php?id=70754&r=notwrong Not enough info: https://bugs.php.net/fix.php?id=70754&r=notenoughinfo Submitted twice: https://bugs.php.net/fix.php?id=70754&r=submittedtwice register_globals: https://bugs.php.net/fix.php?id=70754&r=globals PHP 4 support discontinued: https://bugs.php.net/fix.php?id=70754&r=php4 Daylight Savings: https://bugs.php.net/fix.php?id=70754&r=dst IIS Stability: https://bugs.php.net/fix.php?id=70754&r=isapi Install GNU Sed: https://bugs.php.net/fix.php?id=70754&r=gnused Floating point limitations: https://bugs.php.net/fix.php?id=70754&r=float No Zend Extensions: https://bugs.php.net/fix.php?id=70754&r=nozend MySQL Configuration Error: https://bugs.php.net/fix.php?id=70754&r=mysqlcfg