Online PHP editor | refs for fDsW5

<?php $data = [ "date" => 1554328800, "events" => [130, 131, 163], "tags" => [4, "1,3,4", "1,3"] ]; // 1. List the events per individual tag foreach($data["tags"] as $i => $val) { $vals = explode(",", $val); foreach($vals as $val) { $eventsByTag[$val][] = $data["events"][$i]; } } // 2. List the tags per set of events foreach($eventsByTag as $tag => $events) { sort($events, SORT_NUMERIC); $tagsByEvents[implode(",", $events)][] = $tag; } // 3. produce the result foreach($tagsByEvents as $events => $tags) { $events = explode(",", $events); if (count($tags) == 1) $tags = $tags[0]; $result[] = [ "date" => $data["date"], "events" => $events, "tags" => $tags ]; } print_r($result);