note 48583 added to function.array-diff

Here is some code to take the difference of two arrays. It allows custom modifications like prefixing with a certain string (as shown) or custom compare functions. <?php // returns all elements in $all which are not in $used in O(n log n) time. // elements from $all are prefixed with $prefix_all. // elements from $used are prefixed with $prefix_used. function filter_unused( $all, $used, $prefix_all = "", $prefix_used = "" ) { $unused = array(); // prefixes are not needed for sorting sort( $all ); sort( $used ); $a = 0; $u = 0; $maxa = sizeof($all)-1; $maxu = sizeof($used)-1; while( true ) { if( $a > $maxa ) { // done; rest of $used isn't in $all break; } if( $u > $maxu ) { // rest of $all is unused for( ; $a <= $maxa; $a++ ) { $unused[] = $all[$a]; } break; } if( $prefix_all.$all[$a] > $prefix_used.$used[$u] ) { // $used[$u] isn't in $all? $u++; continue; } if( $prefix_all.$all[$a] == $prefix_used.$used[$u] ) { // $all[$a] is used $a++; $u++; continue; } $unused[] = $all[$a]; $a++; } return $unused; } ?> ---- Manual Page -- http://www.php.net/manual/en/function.array-diff.php Edit -- http://master.php.net/manage/user-notes.php?action=edit+48583 Delete -- http://master.php.net/manage/user-notes.php?action=delete+48583&report=yes Reason: bad code -- http://master.php.net/manage/user-notes.php?action=delete+48583&report=yes&reason=bad+code Reason: spam -- http://master.php.net/manage/user-notes.php?action=delete+48583&report=yes&reason=spam Reason: useless example -- http://master.php.net/manage/user-notes.php?action=delete+48583&report=yes&reason=useless+example Reason: contains commercial links -- http://master.php.net/manage/user-notes.php?action=delete+48583&report=yes&reason=contains+commercial+links Reason: useless note -- http://master.php.net/manage/user-notes.php?action=delete+48583&report=yes&reason=useless+note Reject -- http://master.php.net/manage/user-notes.php?action=reject+48583&report=yes Search -- http://master.php.net/manage/user-notes.php