the code i gave was for example purposes only, not intended for you to use verbatum
like i said, when you open the detail page in the browser, make note of the URL Parameter that is used to pass the id,
i gave an example for the URL variable named "id"
looking at the code on your page, the URL variable is named UserID, so the code for the link needs to be:
<a href="detail.php?UserID=<?php echo(isset($_GET['UserID'])?$_GET['UserID']:""); ?>&report=true">Report content</a></div>