How to instantiate an helper class from my custom module in a test program in the directory at the same level as the root of Magento?

Question

With the code below, I'm trying to instantiate an helper class from my custom module.

// Sanitize the $_GET[] value
// Create an object of the order loaded with the $order_id passed as query string.
$orderId = htmlspecialchars($_GET["order_id"]);
$order = $objectManager->create('Magento\Sales\Model\Order')->loadByIncrementID($orderId);

// Instantiate app/code/Perfectmakeupmirrors/Order/Helper/Data.php
// call assemble_order_info(Order $order)
$helper = $objectManager->get('\app\code\Perfectmakeupmirrors\Order\Helper\Data');

Please guide me on the right way to do it.

Answer 1

To retrieve a helper class from your custom module, replace your code:

$helper = $objectManager->get('\app\code\Perfectmakeupmirrors\Order\Helper\Data');

to

$helper = $objectManager->get('Perfectmakeupmirrors\Order\Helper\Data');

Btw, the Original Poster would like to use his code for testing purposes, so we can use ObjectManager. We should not (almost never) use ObjectManager in real code, there is a post discussing this To use or not to use the ObjectManager directly?