Load category in ajax

Category loader

add_action( 'wp_ajax_dokan_fetch_product_child_category', 'dokan_fetch_product_child_category' );

function dokan_fetch_product_child_category() {
    if ( ! isset( $_REQUEST['_wpnonce'] ) || ! wp_verify_nonce( $_REQUEST['_wpnonce'], 'marketica-child-theme-nonce' ) ) {
        wp_send_json_error( __( 'Nonce Verfication faild', 'dokan' ) );
    }

    $category_id = ( isset( $_POST['category'] ) && ! empty( $_POST['category'] ) ) ? $_POST['category'] : '';

    if ( empty( $category_id ) ) {
        wp_send_json_error( 'No Category Selected', 'dokan' );
    }

    $categories = get_terms( 'product_cat', array(
        'orderby'    => 'count',
        'hide_empty' => 0,
        'parent'     => $category_id,
    ) );
    if ( empty( $categories ) ) {
        wp_send_json_error(__( 'No Category Found', 'dokan' ) );
    }
    ob_start();
    ?>
    <div class="dokan-category-wrapper" style="margin-top:20px">
        <select class="dokan_product_category dokan-form-control chosen" name="product_cat[]" id="product_cat" style="height: 26px; margin-top: 20px;" data-placeholder="<?php _e('Select a category', 'dokan' ); ?>">
            <option value=""></option>
            <?php foreach ( $categories as $key => $category ) : ?>
                <option value="<?php echo $category->term_id ?>"><?php echo $category->name; ?></option>
            <?php endforeach ?>
        </select>
    </div>
    <?php
    $content = ob_get_clean();

    wp_send_json_success( $content );
}

// add_action( 'dokan_product_updated', 'dokan_map_category_ids_save', 59 );
add_action( 'dokan_process_product_meta', 'dokan_map_category_ids_save', 59 );
add_action( 'dokan_new_product_added', 'dokan_map_category_ids_save', 59 );

function dokan_map_category_ids_save( $product_id ) {
    if ( ! is_user_logged_in() ) {
        return;
    }

    if ( ! dokan_is_user_seller( get_current_user_id() ) ) {
        return;
    }

    if ( isset( $_POST['product_cat'] ) ) {
        update_post_meta( $product_id, '_categroy_hirerchy_ids', $_POST['product_cat'] );
    }
}