$_GET always returning null

Question

I have a Wordpress site calling a .php file on our server using a shortcode. The goal is to return query parameters to a Wordpress form using hidden fields.

Here is the problem: $_GET['param'] doesn't seem to work for any key 'param'. For example, I have the following code in my shortcode function:

ChromePhp::log('Test Output');
ChromePhp::log($_GET['test']);
ChromePhP::log($_SERVER['QUERY_STRING']);

I have installed a PHP logging plugin so I can see the PHP output from the Chrome javascript console. When I go to the URL mysite.com/properpage?test=testparam The output is:

Test Output
null
null

I'm not sure if it's relevant, but when I go to the url with the proper query params (?test=testparam), the url resets itself and clears the query params off the end.

I feel like I'm missing something simple. Or Wordpress may be blocking query params somewhere for this page so it clears the url?

As suggested by steve in the comment, I added the following to the functions.php file where my shortcode function is:

add_action('init','wpse46108_register_param');
function wpse46108_register_param() { 
    global $wp; 
    $wp->add_query_var('test'); 
}

But

ChromePhp::log(get_query_var('test'));

still has empty output when I add the query param ?test=test.

Answer 1

使用get_query_var（）函数获取查询字符串变量