Online PHP editor | refs for jMEP2

<?php $a = [ [ 'ID' => 3, 'Username' => 'TomC', 'Project_Name' => 'Inventory' ], [ 'ID' => 4, 'Username' => 'JakeP', 'Project_Name' => 'Inventory' ], [ 'ID' => 2, 'Username' => 'TomC', 'Project_Name' => 'Stocks' ],[ 'ID' => 1, 'Username' => 'Tomc', 'Project_Name' => 'Stocks' ] ]; $b = array_unique( array_column($a, 'Username') ); print_r($b);