note 78573 added to function.array-diff

A wee idiom for KEEPING only those elements of an array $a that appear in an array $b (without introducing any elements of $b that do not appear in $a). <?php array_diff($a, array_diff($a, $b)) ?> And for mr dot kschan at gmail dot com: if it's the SYMMETRIC difference you want, (A-B typically is not equal to B-A; consider the case when A and B are integers), there is Viking Coder's comment 04-Jan-2006, or there is the alternative: <?php function symmetric_array_diff($array1, $array2) { return array_diff(array_merge($array1, $array2), array_intersect($array1, $array2)); } ?> Viking Coder's expression and mine are equivalent: (A-B)u(B-A) == (AuB)-(AnB). They're probably about equal in efficiency. ---- Server IP: 203.89.181.186 Probable Submitter: 60.234.168.92 ---- Manual Page -- http://www.php.net/manual/en/function.array-diff.php Edit -- https://master.php.net/note/edit/78573 Del: integrated -- https://master.php.net/note/delete/78573/integrated Del: useless -- https://master.php.net/note/delete/78573/useless Del: bad code -- https://master.php.net/note/delete/78573/bad+code Del: spam -- https://master.php.net/note/delete/78573/spam Del: non-english -- https://master.php.net/note/delete/78573/non-english Del: in docs -- https://master.php.net/note/delete/78573/in+docs Del: other reasons-- https://master.php.net/note/delete/78573 Reject -- https://master.php.net/note/reject/78573 Search -- https://master.php.net/manage/user-notes.php