Online PHP editor | refs for suPr4

<?php $arr = array ( 0 => array ( 0 => array ( 'personNum' => 2, 'type' => 'comment', 'datetime' => '2019-05-15 11:29:45' ), 1 => array ( 'personNum' => 3, 'type' => 'status', 'datetime' => '2019-05-26 15:59:53' ) ), 1 => array ( 0 => array ( 'personNum' => 3, 'type' => 'status', 'datetime' => '2019-05-26 15:59:53' ), 1 => array ( 'personNum' => 4, 'type' => 'status', 'datetime' => '2019-05-26 16:04:24' ), ) ); array_walk($arr, function (&$v) { array_multisort(array_column($v, 'datetime'), SORT_DESC, $v); }); usort($arr, function ($a, $b) { return strcmp(max(array_column($b, 'datetime')), max(array_column($a, 'datetime'))); }); print_r($arr);