forminator_post_acf_categories_and_tags.php

<?php
/**
 * Plugin Name: [Forminator] Using ACF Fields as Categories and Tags
 * Plugin URI: https://wpmudev.com/
 * Description: Allow Forminator create a post and use the values on ACF fields for Categories and Tags.Categories and Tags will be created if does'nt exist.
 * Author: Alfredo Galano Loyola @ WPMUDEV
 * Author URI: https://wpmudev.com/
 * License: GPLv2 or later
 *
 * @package Forminator_ACF_Fields_Categories_and_Tags
 */
defined( 'ABSPATH' ) || exit;
function wpmudev_forminator_intercept_data_post_info( $post, $field, $data ){
    /*Custom Categories need to be and array if integers(categories ID) like array(12, 5, 7)*/
    $custom_categories = array();
    /*Custom tags need to be string, like "Tag1,Tag2,Tag3" */
    $custom_tags = "";
    /* Getting the ACF field DATA from the Forminator Pro Custom post, it is a list of fields with name and value*/
    $acf_data = $data['post-custom'];
    /*Checking the ACF list of fields to find the one needed for Categories and Tags */
    foreach ($acf_data as $key => $acf_field) {
        /* Checking the ACF fields, I used custom_categories as the name of my field for Categories */
        if ($acf_field['key']=="custom_categories") {
            /*Converting the Data in a list of categories like array("Cat1","Cat2","Cat3") */
            $categories = explode(",",str_replace(', ', ',', $acf_field['value'])); 
            /*Looping the list of categories selected for that post */
            foreach ($categories as $category) {
                /*Adding categories to the Database if not exist, $cat_id will handle the ID value of the category */
                $cat_id = wp_create_category($category);
                if ($cat_id > 0) {
                    /*Creating the list of ID for my custom categories for the post */
                    $custom_categories[] = (int) $cat_id;
                }
            }
        }
        /*Checking the ACF field related to the tags */
        if ($acf_field['key']=="custom_tags") {
            /*Cleaning white space near the comma and assigning the custom tags */
            $custom_tags = str_replace(', ', ',', $acf_field['value']);
        }
    }
    /* Adding the Categories to the post data */
    $post['post_category'] = $custom_categories;
    /* Adding the Tags to the post data */
    $post['tags_input'] = $custom_tags;
    /*The post data is returned to being added to the Database as a new post */
    return $post;
}
add_filter('forminator_post_data_post_info','wpmudev_forminator_intercept_data_post_info', 999, 3 );