Add custom data Import and Export to Developers in Product CSV Importer and Exporter

guides/woocommerce-product-to-wordpress.md

@@ -38,3 +38,107 @@ Wait until the Importer is finished. Do not refresh or touch the browser while i
 
 ## That's it!
 Your products are now imported - you can view them under 'Products' in the main admin menu.
+
+# Add or Import Custom Data
+
+If you have another WordPress site with WooCommerce products that you would like to migrate, it is definitely something you can do. In your current installation, your products may have custom fields and you want to migrate this data to your new WooCommerce and WordPress installation. You can choose to add those fields so that they are recognizable and saved by the WooCommerce Product CSV Importer and Exporter. Below is a example for developers to add columns to the WooCommerce importer.
+
+This guide will walk you through using the importer and exporter and will also detail how to add custom import and export columns for developers.
+
+# Adding Custom Import Columns (for Developers)
+
+It is a straightforward process to add support for custom columns to the importer. The following example breaks down the process:
+
+```php
+/**
+ * Register the 'Custom Column' column in the importer.
+ *
+ * @param array $options
+ * @return array $options
+ */
+function add_column_to_importer( $options ) {
+
+	// column slug => column name
+	$options['custom_column'] = 'Custom Column';
+
+	return $options;
+}
+add_filter( 'woocommerce_csv_product_import_mapping_options', 'add_column_to_importer' );
+
+/**
+ * Add automatic mapping support for 'Custom Column'. 
+ * This will automatically select the correct mapping for columns named 'Custom Column' or 'custom column'.
+ *
+ * @param array $columns
+ * @return array $columns
+ */
+function add_column_to_mapping_screen( $columns ) {
+
+	// potential column name => column slug
+	$columns['Custom Column'] = 'custom_column';
+	$columns['custom column'] = 'custom_column';
+
+	return $columns;
+}
+add_filter( 'woocommerce_csv_product_import_mapping_default_columns', 'add_column_to_mapping_screen' );
+
+/**
+ * Process the data read from the CSV file.
+ * This just saves the value in meta data, but you can do anything you want here with the data.
+ *
+ * @param WC_Product $object - Product being imported or updated.
+ * @param array $data - CSV data read for the product.
+ * @return WC_Product $object
+ */
+function process_import( $object, $data ) {
+
+	if ( ! empty( $data['custom_column'] ) ) {
+		$object->update_meta_data( 'custom_column', $data['custom_column'] );
+	}
+
+	return $object;
+}
+add_filter( 'woocommerce_product_import_pre_insert_product_object', 'process_import', 10, 2 );
+```
+
+## Adding Custom Export Columns (for Developers)
+
+It is a straightforward process to add support for custom columns to the exporter. The following example breaks down the process:
+
+```php
+/**
+ * Add the custom column to the exporter and the exporter column menu.
+ *
+ * @param array $columns
+ * @return array $columns
+ */
+function add_export_column( $columns ) {
+
+	// column slug => column name
+	$columns['custom_column'] = 'Custom Column';
+
+	return $columns;
+}
+add_filter( 'woocommerce_product_export_column_names', 'add_export_column' );
+add_filter( 'woocommerce_product_export_product_default_columns', 'add_export_column' );
+
+/**
+ * Provide the data to be exported for one item in the column.
+ *
+ * @param mixed $value (default: '')
+ * @param WC_Product $product
+ * @return mixed $value - Should be in a format that can be output into a text file (string, numeric, etc).
+ */
+function add_export_data( $value, $product ) {
+	$value = $product->get_meta( 'custom_column', true, 'edit' );
+	return $value;
+}
+// Filter you want to hook into will be: 'woocommerce_product_export_product_column_{$column_slug}'.
+add_filter( 'woocommerce_product_export_product_column_custom_column', 'add_export_data', 10, 2 );
+```
+
+
+# ¿You have problems or questions about the Product CSV Importer & Exporter?
+
+You can see the official documentation in the following github repository: https://github.com/woocommerce/woocommerce/wiki/Product-CSV-Importer-&-Exporter
+