I have code:

class some{

     public function run(){

            add_filter('query_vars', array( $this, 'addPar'));   

     public function addPar($vars){

      $vars[] = "my_par"; 
      return $vars;


    public function some_body(){

     if(isset( get_query_var('my_par')) {

      $value = get_query_var('my_par'); 

      echo $value;


    echo '<li><a href="'.esc_url(add_query_arg(array('my_par' => '4'))).'">></a></li>'; 



in my plugin i call:

$action = new some();

Nothing should appear on the start, but after clicking on the link the variable should already be registered but I get null.

From `var_dump(get_query_var('my_par')):

  public 'query' => null
  public 'query_vars' => 
    array (size=0)
  public 'tax_query' => null
  public 'meta_query' => boolean false
  public 'date_query' => boolean false


my_par is not registered.

  • I change little code but idea is the same - after click link variable is not registered in WP Query in "public query_vars". – polyman Apr 3 at 11:41
  • Can you see something in debug.log? – huraji Apr 3 at 19:05
  • i have define WP_DEBUG, WP_DEBUG_LOG and SCRIPT_DEBUG as TRUE but i not have debug.log file in /wp-content. Plugin WP Live Debug display nothing. I testing my plugin in localhost. – polyman Apr 3 at 19:17
  • Ok, I'd suggest to fix this issue before, it could be really helpful. – huraji Apr 3 at 19:23
  • Debug display nothing. I testing my plugin in localhost. – polyman Apr 3 at 19:24

some_body needs to be run as an action on pre_get_posts.

Here's an example of the entire process of adding new query vars.

Pay extra attention to myplugin_pre_get_posts:

function myplugin_pre_get_posts( $query ) {
    $city = get_query_var( 'city' );
add_action( 'pre_get_posts', 'myplugin_pre_get_posts', 1 );
  • can you look in my new code? – polyman Apr 4 at 22:24
  • I just saw admin.php in your code. If this is something you're doing in the WordPress admin, this is not the right way to do it. Take a look at wordpress.stackexchange.com/questions/91693/… and the WordPress Codex for Admin Pages: codex.wordpress.org/Adding_Administration_Menus – MikeNGarrett Apr 5 at 13:50
  • I call "admin" in title question. I have menu and now in some in content in admin panel in my plugin i must get variables from $_GET, and of course i can do it $_GET['some'] but i want know how do it correctly. – polyman Apr 5 at 17:02
  • Yes, I understand. Adding query vars is not what you should be doing here. That's for matching patterns on the front-end to map url structure to particular query arguments. This is not intended use for any of this. – MikeNGarrett Apr 5 at 18:33

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