PHP include() displaying number 1 after print

I just encountered a weird little quirk of PHP that I spent awhile trying to resolve, so I'm posting this as a Google search turns up nothing. 

When including a .php file in the midst of an html/view file using the include() function:

<?= include('myfile.php') ?>

Was producing a number '1' located after the end of include. The issue turns out to be a bug / feature or using short tags: 

<?= 

as opposed to: 

<?php include('myfile.php'); ?>

the problem is that the short translates to: 

<?php echo include('myfile.php'); ?>

which also produces the '1' hopefully this helps someone.