Add GET based filtering of WordPress queries.

get-filtering.php

<?php
/**
 * Allow filtering of index/archives by GET
 * Example) Adding ?sort=-date will sort posts descending by date.
 * Possible Values: https://codex.wordpress.org/Class_Reference/WP_Query#Order_.26_Orderby_Parameters
 */
add_action('pre_get_posts', function ($query) {
  if( $query->is_main_query() ) {
    $sort = "relevance";
    $order = "DESC";

    if ( isset($_GET['sort']) ) {
      $sort = $_GET['sort'];
      $order = substr($sort, 0, 1);

      if($order == "-") {
        $order = "DESC";
        $sort = ltrim($sort, '-');
      } else {
        $order = 'ASC';
      }
    }
    
    $query->set( 'orderby', $sort );
    $query->set( 'order', $order );
  }
});

• Possbile Values
• Use in conjuction with this autosubmit filter for easy filter toggle.