Forminator - check and prevent duplicate entries

<?php
/**
* Plugin Name: [Forminator Pro] - Prevent duplicate entries
* Plugin URI: https://premium.wpmudev.org/
* Description: Allow to filter values and prevent duplicate entries for selected forms and fields (as of 1.8.1)
* Author: Alessandro Kaounas @ WPMUDEV
* Author URI: https://premium.wpmudev.org/
* License: GPLv2 or later
*/
if ( ! defined( 'ABSPATH' ) ) {
    exit;
}

if ( ! class_exists( 'WPMUDEV_Forminator_Duplicate_Entries' ) ) {
    class WPMUDEV_Forminator_Duplicate_Entries {
        private static $_instance = null;
        private $fields_to_check = array(
            // User defined - One form per line with selected fields (must exists in forms' settings)
            // Example: $form_id => array('field-1', 'field-2', ..., 'field-n')
            22246 => array('phone-3', 'email-4')
        );
        public static function get_instance() {
            if( is_null( self::$_instance ) ){
                self::$_instance = new WPMUDEV_Forminator_Duplicate_Entries();
            }
            return self::$_instance;
        }
        private function __construct() {
            add_filter( 'forminator_custom_form_submit_errors', array( $this, 'forminator_avoid_duplicate_entries'), 999, 3 );
        }
        function forminator_avoid_duplicate_entries($entry, $form_id, $field_data_array){
            if( empty( $this->fields_to_check[$form_id] ) ) return $entry;
            global $wpdb;
            $duplicate = false;
            $frmt_form_entry = $wpdb->prefix . 'frmt_form_entry';
            $frmt_form_entry_meta = $wpdb->prefix . 'frmt_form_entry_meta';
            foreach($this->fields_to_check as $form){
                foreach($form as $field){
                    $field_key = array_search($field, array_column($field_data_array, 'name'));
                    if($field_key === false) continue;
                    $sql_query = "SELECT COUNT(`meta_value`) FROM `$frmt_form_entry_meta` WHERE `entry_id` IN (SELECT `entry_id` FROM `$frmt_form_entry` WHERE `form_id` = $form_id) AND `meta_key` = '$field' AND `meta_value` = '%s' GROUP BY `meta_value`;";
                    if( $wpdb->query( $wpdb->prepare( $sql_query, $field_data_array[$field_key]['value'] ) ) ){
                        $duplicate = true;
                        break;
                    }
                }
            }
            if(!$duplicate) return $entry;
            // Just in case something has changed in database schema
            if(($wpdb->get_var("SHOW TABLES LIKE '$frmt_form_entry';") != $frmt_form_entry) ||
            ($wpdb->get_var("SHOW TABLES LIKE '$frmt_form_entry_meta';") != $frmt_form_entry_meta)) return $entry;
            $response = array(
                'message' => __( 'The survey with similar data has been already submitted / A felmérés a megadott adatokkal már rögzítésre került', 'forminator' ),
                'success' => false,
                'errors'  => array(),
                'behav'   => ''
            );
            echo wp_send_json(['success' => false, 'data' => $response]);
            return $entry;
        }
    }
    if ( ! function_exists( 'wpmudev_forminator_avoid_duplicate_entries' ) ) {
        function wpmudev_forminator_avoid_duplicate_entries() {
            return WPMUDEV_Forminator_Duplicate_Entries::get_instance();
        };
        add_action( 'plugins_loaded', 'wpmudev_forminator_avoid_duplicate_entries', 99 );
    }
}