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<?php $teacherActiveGroupNameData = [ "100" => ["name" => "1 A"], "200" => ["name" => "1 B"], "300" => ["name" => "1 C"], "400" => ["name" => "1 D"], ]; $activeGroups = [ "user1" => ["100" , "200"], "user2" => ["100" , "300"], "user3" => ["100" , "200","400"], ]; $r = []; foreach($activeGroups as $k => $v){ foreach($v as $ik => $iv){ $r[$k][] = $teacherActiveGroupNameData[$iv]['name']; } } echo '<pre>'; print_r($r);
Output for 7.1.25 - 7.1.30, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.25, 8.4.1 - 8.4.12
<pre>Array ( [user1] => Array ( [0] => 1 A [1] => 1 B ) [user2] => Array ( [0] => 1 A [1] => 1 C ) [user3] => Array ( [0] => 1 A [1] => 1 B [2] => 1 D ) )

preferences:
42.82 ms | 408 KiB | 5 Q