'Red', 'WEIGHT' => 20 ], [ 'COLOR' => 'Red', 'WEIGHT' => 25 ], [ 'COLOR' => 'Red', 'WEIGHT' => 30 ], [ 'COLOR' => 'Green', 'WEIGHT' => 20 ], [ 'COLOR' => 'Green', 'WEIGHT' => 25 ], [ 'COLOR' => 'Green', 'WEIGHT' => 30 ] ]; $out = []; foreach ($arr as $a) { $out[$a['COLOR']][] = $a['WEIGHT']; } ?> $arr) { ?>