How to pass a PHP $_GET variable and fetch/output it?
get_query_var() only works with the Core WP_Query object: Retrieve public query variable in the WP_Query class of the global $wp_query object. https://codex.wordpress.org/Function_Reference/get_query_var Your mistake is a simple PHP one: The key is foo, not bar. $foo = $_GET[‘foo’]; echo $foo; But please do not echo user supplied data to the page without sanitizing it.