Disable WordPress search

functions.php

<?php
// Yoink: https://www.wpbeginner.com/wp-tutorials/how-to-disable-the-search-feature-in-wordpress/
// Tested on WordPress: 5.9.3
// PHP: 8.0

/*
  Instead of going to a search page, show 404 instead
*/
function wpb_filter_query( $query, $error = true ) {
    if ( is_search() ) {
        $query->is_search = false;
        $query->query_vars['s'] = false;
        $query->query['s'] = false;
    if ( $error == true )
        $query->is_404 = true;
    }
}
add_action( 'parse_query', 'wpb_filter_query' );

/*
  This removes the search widget from the UI.
  But only for PHP 7.x and below, this will NOT work for PHP 8.x
*/
// add_filter( 'get_search_form', create_function( '$a', "return null;" ) );
// function remove_search_widget() {
//     unregister_widget('WP_Widget_Search');
// }
// add_action( 'widgets_init', 'remove_search_widget' );