Add product attribute to email in php.

Hi!
First. Lovely plugin. Its easy to use and great looking, super easy to customize. But I do need help with on thing. I would love if any one of you could take a look at this 🙂

I would like to add an product attribute ( “shelf” ) to the email, but cant get the php right.
Picture of email

My crappy php-code :/

My code in sublime

echo ‘<br/><small>shelf: ‘ . nl2br( $_product->get_attribute( ‘shelf’ ) ) . ‘</small>’;
I got an error about some definition error.
The php file is btw email-order-items.php

This is for being able to find items in the warehouse very quickly, any other ideas or solutions are welcome! Biggest thanks in Advance 🙂

The page I need help with: [log in to see the link]