Your function will only be called when there is something in$_GET['calc_submit_1']. Means, when you submit the form, your function is triggered. When you refresh the page, and $_GET['calc_submit_1'] is empty, it won’t triggered. When FB checks for OG, FB will not submit your form and your function will not be triggered.
You can use add_option to save something in to database on form submit, and check that, instead of $_GET['calc_submit_1'].
