If statement within an array declaration …is that possible? [duplicate]

Answer 1

NO. Simple as that.

Do:

$product_option_value_data[] = array(
    'product_option_value_id' => $product_option_value['product_option_value_id'],
    'name'                    => $product_option_value_description_query->row['name'],
    'price'                   => $product_option_value['price'],
    'prefix'                  => $product_option_value['prefix']
);

if (isset($product_option_value_description_query->row['smallimage'])) {
     $product_option_value_data[count($product_option_value_data) - 1]['smallimage'] = $product_option_value_description_query->row['smallimage'],
     // I'm not sure if you meant to have that [] in your declaration above
     // You may need to drop it, in which case the line would be:
     // $product_option_value_data['smallimage'] = $product_option_value_description_query->row['smallimage'],
}