get_query_var always returns the default value

Question

I am really new to wordpress, and I am trying to build a page that updates the database with given arguments. For example, if the client application calls https://codonmaster.000webhostapp.com/ranking.php?scoretime=30&nickname=hellooo&score=100 , then I want to insert a column ('hellooo',30,100) in my database.

However, I am stuck getting the query vars to my php code. The page always shows

defaultname,1566820333(current timestamp),0 

Yes, the default values. Where should I change to make this page acknowledge needed variables?

My code is below:

<?php
 require_once(dirname(__FILE__) . '/wp-config.php');
 $wp->init();
 $wp->parse_request();
 $wp->query_posts();
 $wp->register_globals();
 $wp->send_headers();


function themeslug_query_vars( $qvars ) {
    $qvars[] = 'scoretime';
    $qvars[] = 'nickname';
    $qvars[] = 'score';
   return $qvars;
}
add_filter( 'query_vars', 'themeslug_query_vars' );

$scoretime = get_query_var( 'scoretime', ''.time());
$nickname = get_query_var( 'nickname', 'defaultname' );
$score = get_query_var('score', '0');
echo "{$nickname},{$scoretime},{$score}";

Answer 1

In WordPress, query vars are not what you think they are. They are the arguments for the global WP_Query object which processes the main page request. Check the docs for more information.

What you need in that particular case is to check the $_GET parameters on the page load.

For example:

$scoretime = filter_input( INPUT_GET, 'scoretime', FILTER_SANITIZE_NUMBER_INT ) ?: (string) time();
$score = filter_input( INPUT_GET, 'score', FILTER_SANITIZE_NUMBER_INT ) ?: '0';
$nickname = filter_input( INPUT_GET, 'nickname', FILTER_SANITIZE_STRING ) ?: 'defaultname';

Please note that I have accessed them using filter_input() method, which is a good practice to do a sanitization of the inputs, especially if you plan on inserting them in the database.

Also, I have added the default values after the ?:, which is a short ternary operator, and assigns the left if its value is truthy.