Online PHP editor | refs for bdgPl

<?php $rows = [ 100 => [ ['product_id' => 101, 'name' => ''], ['product_id' => 102, 'name' => ''], ['product_id' => 103, 'name' => ''], ], 200 => [ ['product_id' => 201, 'name' => ''], ['product_id' => 202, 'name' => ''], ], 300 => [ ['product_id' => 301, 'name' => ''], ['product_id' => 302, 'name' => ''], ['product_id' => 303, 'name' => ''], ['product_id' => 304, 'name' => ''], ] ]; var_export( array_merge( ...array_map( function() { return array_filter( func_get_args() ); }, ...$rows ) ) );