[WP] Search helpers + include all meta fields in default search query

search.php

<?php defined('ABSPATH') or header('Location: /');
/**
 * Fix search when using smart quotes. Downgrade to straight double quotes.
 */
add_filter('pre_get_posts',  'filter_smart_quote_queries', 10, 1);
add_action('pre_get_posts',  'exclude_posts_from_search');


/**
 * Add custom fields data to global WP search
 *
 * @reference https://generatepress.com/forums/topic/how-can-i-include-advanced-custom-fields-data-in-search-results/
 */
add_filter('posts_join',     'acf_search_join');
add_filter('posts_where',    'acf_search_where');
add_filter('posts_distinct', 'acf_search_distinct');


/**
 * Fix (convert) "smart" quotes
 */
function filter_smart_quote_queries($query) {
  if(!empty($query->query['s'])) {
    $search_term = $query->query['s'];
    $search_term = str_replace(array('"', '"', '\&#34;'), '"', $search_term); // Smart (curly) double quote > straight double quote
    unset($query->query['s']);
    $query->set('s', $search_term);
  }
  
  return $query;
}


/**
 * Exclude from search
 */

function exclude_posts_from_search($query){
  if($query->is_main_query() && is_search()){
     $post_ids = get_field('exclude_from_search', 'option'); //Exclude posts by ID
     $query->set('post__not_in', $post_ids);
  }
}


/**
 * Join posts and postmeta tables
 *
 * @see http://codex.wordpress.org/Plugin_API/Filter_Reference/posts_join
 */
function acf_search_join($join) {
  global $wpdb;

  if(is_search()) {
    $join .=' LEFT JOIN '.$wpdb->postmeta. ' ON '. $wpdb->posts . '.ID = ' . $wpdb->postmeta . '.post_id ';
  }

  return $join;
}


/**
 * Modify the search query with posts_where
 *
 * @see http://codex.wordpress.org/Plugin_API/Filter_Reference/posts_where
 */
function acf_search_where($where) {
  global $wpdb;

  if(is_search()) {
    $where = preg_replace(
      "/\(\s*".$wpdb->posts.".post_title\s+LIKE\s*(\'[^\']+\')\s*\)/",
      "(".$wpdb->posts.".post_title LIKE $1) OR (".$wpdb->postmeta.".meta_value LIKE $1)", 
      $where
    );
  }

  return $where;
}


/**
* Prevent duplicates
*
* @see http://codex.wordpress.org/Plugin_API/Filter_Reference/posts_distinct
*/
function acf_search_distinct($where) {
  global $wpdb;

  if(is_search()) {
    return "DISTINCT";
  }

  return $where;
}