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<?php $rows = [ ['cat' => 'guest', 'name' => 'name_one', 'y' => '2016', 'q' => '2', 'st' => 1], ['cat' => 'guest', 'name' => 'name_one', 'y' => '2017', 'q' => '3', 'st' => 2], ['cat' => 'guest', 'name' => 'name_two', 'y' => '2017', 'q' => '1', 'st' => 1], ['cat' => 'guest', 'name' => 'name_two', 'y' => '2017', 'q' => '2', 'st' => 2], ]; $data = []; foreach ($rows as $row) { $link = &$data; foreach (['cat', 'name', 'y'] as $field) { if (!isset($link[$row[$field]])) $link[$row[$field]] = []; $link = &$link[$row[$field]]; } $link[$row['q']] = $row['st']; unset($link); } print_r($data);
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 7.3.0 - 7.3.30, 7.4.0 - 7.4.23, 8.0.0 - 8.0.11, 8.1rc1 - rc2
Array ( [guest] => Array ( [name_one] => Array ( [2016] => Array ( [2] => 1 ) [2017] => Array ( [3] => 2 ) ) [name_two] => Array ( [2017] => Array ( [1] => 1 [2] => 2 ) ) ) )

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