I was facing same issue but when I added
ini_set('display_errors', 1);
in top of the page, I got below error.
Fatal error: Allowed memory size of 2621440000 bytes exhausted (tried to allocate 12288 bytes)
You can try below code
$orders = $obj->get('Magento\Sales\Model\Order')->getCollection()->setPageSize(10) // only get 10 products
->setCurPage(1);
echo "<pre>";
foreach ($orders as $order) {
print_r($order->getData());
}
echo "</pre>";
This is same method you are using to print data with filter and it is working fine.
There are 2 solutions, you can increase memory limit or select fields that you want in your collection.
In addition, use the $order->debug() method instead of $order->getData(). This will prevent memory leaks.