减少内存消耗，将帖子克隆到多站点网络中的另一个站点

Question

我正在创建一个插件，以将wordpress多站点帖子从一个站点克隆到网络中的另一个站点。

到目前为止，这是我的代码

我只加载帖子ID，而不是整个帖子。

看着分析器，执行脚本时内存使用量继续增加，最终导致max_memory错误

class Cloner {
    private $types = [];

    public $total_posts = 0;

    public $transfer_to;

    function __construct($post_types = null, $transfer_to) {
        $this->types = $this->get_registered_post_types();
        $this->transfer_to = $transfer_to;
        foreach ($this->types as $key => $type) {
            $this->do_transfer_for_post_type($type);
        }
    }

    function do_transfer_for_post_type($type) {
            $posts = $this->get_post_ids_for_transfer($type);
            $type_count = count($posts);

            $this->total_posts = $this->total_posts + $type_count;
            $this->transfer($posts);
            unset ($posts);
    }


    function get_post_ids_for_transfer($post_type) {
        // only get ids to save memory
        $args = array(
            'posts_per_page' => -1,
            'post_type' => $post_type,
            'fields' => 'ids',
            'no_found_rows'          => true,
            'update_post_term_cache' => false,
            'update_post_meta_cache' => false,
            'cache_results'          => false
        );
        $q = new WP_Query($args);
        $posts = $q->posts;
        wp_reset_query();
        return $posts;

    }

    function transfer($posts) {

        foreach ($posts as $id) {
            $this->copy_post_to_blog($id);
        }

    }


    function copy_post_to_blog($post_id) {
        $post = get_post($post_id, ARRAY_A); // get the original post
        $meta = get_post_meta($post_id);
        $post['ID'] = ''; // empty id field, to tell wordpress that this will be a new post
        switch_to_blog($this->transfer_to); // switch to target blog
        $inserted_post_id = wp_insert_post($post); // insert the post
        $this->insert_meta($meta, $inserted_post_id);
        $post = null;
        restore_current_blog(); // return to original blog
    }


    function insert_meta($meta, $post_id) {
        global $wpdb;

        $custom_fields = [];
        $query_string = "INSERT INTO $wpdb->postmeta ( post_id, meta_key, meta_value) VALUES ";
        foreach($meta as $key => $value) {
            array_push($custom_fields, $post_id, $key, $value[0]);
            $place_holders[] = "('%d', '%s', '%s')";
        }
        $query_string .= implode(', ', $place_holders);
        $query = $wpdb->prepare("$query_string ", $custom_fields);
        $wpdb->query( $query );
    }


    function get_registered_post_types() {
        $args = array(
            'public'   => true,
            '_builtin' => false,
         );

         $output = 'names'; // names or objects, note names is the default
         $operator = 'and'; // 'and' or 'or'

         return get_post_types( $args, $output, $operator ); 
    }
}

$cloner = new Cloner(null, 7);

我希望脚本使用相当一致的内存量-如何清理它？