Online PHP editor | output for GEjki

<?php $getTheHistoricData = [ 0 => [ 'DeviceID' => '1', 'DeviceTimestamp' => '2018-09-22 00:00:11', 'LineTemp' => '22.2148', 'LineCurrent' => '232.562', 'RxRSSI' => '0' ], 1 => [ 'DeviceID' => '1', 'DeviceTimestamp' => '2018-09-22 00:00:33', 'LineTemp' => '22.2154', 'LineCurrent' => '234.672', 'RxRSSI' => '0' ], 2 => [ 'DeviceID' => '1', 'DeviceTimestamp' => '2018-09-22 00:00:55', 'LineTemp' => '22.2094', 'LineCurrent' => '233.954', 'RxRSSI' => '0' ] ]; $output = array_map(function($val){ return $val['DeviceID']; }, $getTheHistoricData); var_dump($output);