Online PHP editor | refs for o5K0s

<?php $arr = [ ['id' => '340', 'days' => '1', 'start_date' => '2018-10-12 00:00:00', 'end_date' => '2018-10-13 00:00:00'], ['id' => '346', 'days' => '2', 'start_date' => '2018-10-12 00:00:00', 'end_date' => '2018-10-14 00:00:00'], ['id' => '339', 'days' => '3', 'start_date' => '2018-10-12 00:00:00', 'end_date' => '2018-10-15 00:00:00'], ['id' => '302', 'days' => '4', 'start_date' => '2018-10-12 00:00:00', 'end_date' => '2018-10-16 00:00:00'], ['id' => '308', 'days' => '5', 'start_date' => '2018-10-12 00:00:00', 'end_date' => '2018-10-17 00:00:00'], ['id' => '354', 'days' => '1', 'start_date' => '2018-10-13 00:00:00', 'end_date' => '2018-10-14 00:00:00'], ['id' => '369', 'days' => '1', 'start_date' => '2018-10-14 00:00:00', 'end_date' => '2018-10-15 00:00:00'] ]; usort($arr, function($a, $b){ return $a['days'] <=> $b['days'];}); var_export(array_values(array_column($arr, null, 'start_date')));