Hooks

Put the examples in a small custom plugin or your child theme's functions.php. Folioline's classes live in the Extendiment\Folioline namespace.

The data hooks get

A document ($document in admin, file and email hooks) is an object with id, type (invoice or credit_note), series, sequence, number, order_id, refund_id, parent_id (a credit note's invoice), issue_date (Y-m-d), currency, net_total, tax_total, total, country, vat_number, reverse_charge (bool), data, created_by and created_at.

data is the snapshot: everything the document says, frozen when it was issued. PDF and e-invoice hooks get it as an array ($document or $snapshot):

Key
type, number, issue_at, currency, decimals, language	The document itself.
order	id, number, date, paid_date, payment_method, payment_method_title, transaction_id, customer_id.
delivery_date, due_date, paid	due_date is null when paid.
seller	company, address keys, vat_id, tax_number, registration, email, phone, bank_name, iban, bic, logo_id, footer.
buyer	name, company, address keys, email, phone, vat_number, vat_status, vat_consultation, vat_checked, customer_id.
shipping	Address keys, or null.
tax_country	The country the VAT was charged for (the OSS report's country). A credit note has its invoice's. Not on documents issued before 1.1.2.
reverse_charge, notices	The legal wording printed for the tax categories.
lines	kind (product, shipping, fee, refund), name, sku, product_id, quantity, unit_net, net, discount, tax, gross, rate, category.
taxes	Per category and rate: category, rate, net, tax.
totals	net, tax, gross, discount, rounding.
invoice, reason	A credit note's invoice (id, number, date) and refund reason.
evidence	ip, ip_country, billing_country, or empty.

Amounts are in the order's currency, rounded to its decimals; a credit note's amounts are positive. Tax categories are the EN 16931 codes: S taxed, Z zero-rated, E exempt, AE reverse charge, K intra-EU supply of goods, G export of goods, O outside the scope of EU VAT.

E-invoice formats are zugferd, xrechnung-cii, xrechnung-ubl and peppol; file hooks also use pdf.

Actions

Action	When
folioline_loaded	Folioline has loaded (on plugins_loaded, with WooCommerce active). Its classes and FOLIOLINE_* constants are available.
folioline_activated	Folioline was activated.
folioline_deactivated	Folioline was deactivated.
folioline_settings	The settings page is built ($page, the page slug folioline): add sections and fields with the Settings API. Sections of your own show on a More tab.
folioline_document_issued	A document was issued and has its number ($document, $order).
folioline_file_stored	A document's file was made and stored ($path, $document, $format): the first time it's needed, again after it went missing, or with a new Buyer reference on the order (a new file; the earlier one is kept).
folioline_documents_tab	Print the contents of a tab you added to WooCommerce → Invoices ($tab).
folioline_documents_column	Print a cell of a column you added to the Invoices list ($column, $document).

// Copy every new document's PDF to an archive folder.
add_action( 'folioline_file_stored', function ( $path, $document, $format ) {
	if ( 'pdf' === $format ) {
		copy( $path, '/mnt/archive/' . basename( $path ) ); // the stored name: a new buyer reference never overwrites an earlier file
	}
}, 10, 3 );

Filters

Issuing and numbering

Filter	What it's for
folioline_wants_invoice	Whether an order that reaches an invoice status gets its invoice automatically ($wants, $order). Staff can still issue one by hand.
folioline_document_data	The snapshot before it's frozen ($data, $type, $order, $refund; $refund is null for invoices).
folioline_document_number	The printed number ($number, $type, $sequence, $date), up to 80 characters. The series and its sequence don't change.
folioline_tax_category	A line's tax category ($category, $tax, $virtual, $context). $context has reverse, physical, and the countries seller, buyer (billing) and destination (where goods go: the shipping address's, the store's for local pickup, else the billing address's).
folioline_due_date	When an unpaid invoice is due ($due, $order, $issued; Y-m-d dates). Never before the invoice's date. Wholesaleline's orders on account use it.
folioline_notices	The legal wording printed on a document ($notices, $categories).

// No automatic invoices for wholesale orders: staff issue them by hand.
add_filter( 'folioline_wants_invoice', function ( $wants, $order ) {
	return $wants && ! $order->get_meta( '_is_wholesale' );
}, 10, 2 );

VAT

Filter	What it's for
folioline_vat_exempt	Whether VAT comes off for a customer ($exempt, $number, $country, $status, $reason, $delivery). $status is valid, invalid, pending (VIES unreachable) or unchecked. $reason says why a number can't take VAT off (format, domestic, non_eu, mismatch, seller, delivered), '' when it can. $delivery is the country the goods are delivered to, '' when there are none.
folioline_vies_result	VIES's answer before Folioline uses and caches it ($result, $number): status (valid, invalid, unavailable), number, name, address, consultation, checked (UTC), error, cached.

PDFs

Filter	What it's for
folioline_pdf_template	The PHP template a PDF is made from ($template, $document): an absolute path.
folioline_pdf_css	The PDF's stylesheet ($css, $document), in mPDF's CSS subset.
folioline_mpdf_config	mPDF's configuration ($config, $document). Keep PDFA and PDFAversion as they are.
folioline_pdf_embed_xml	Whether PDFs carry the Factur-X XML ($embed, $document); default true.
folioline_missing_extensions	The PHP extensions counted as missing for PDFs ($missing).

E-invoices

Filter	What it's for
folioline_buyer_reference	The buyer reference, BT-10 ($reference, $snapshot, $format); default the Buyer reference typed on the order, else the order number.
folioline_electronic_address	A party's electronic address, BT-34 / BT-49 ($endpoint, $role, $snapshot, $format): [ 'scheme' => …, 'id' => … ]. $role is seller or buyer. Default: for Peppol, the VAT number under its country's scheme; otherwise the email address (scheme EM).
folioline_payment_means	Payment instructions ($payment, $snapshot, $format): code (UNCL4461), name, reference, iban, bic, account_name, terms.
folioline_einvoice_model	All the business terms before the XML is written ($model, $snapshot, $format).
folioline_einvoice_problems	What keeps a document from being written in a format ($problems, $snapshot, $format): messages for the store owner; any message stops the file.

// A Leitweg-ID a checkout field plugin keeps on the order, when staff didn't type one.
add_filter( 'folioline_buyer_reference', function ( $reference, $snapshot ) {
	$order = wc_get_order( $snapshot['order']['id'] );
	if ( ! $order || '' !== $order->get_meta( '_folioline_buyer_reference' ) ) {
		return $reference;
	}
	$id = $order->get_meta( 'leitweg_id' );
	return $id ? $id : $reference;
}, 10, 2 );

// A Peppol participant ID (GLN) for the seller.
add_filter( 'folioline_electronic_address', function ( $endpoint, $role, $snapshot, $format ) {
	if ( 'seller' === $role && 'peppol' === $format ) {
		return array( 'scheme' => '0088', 'id' => '4035811991021' );
	}
	return $endpoint;
}, 10, 4 );

The buyer reference and electronic address are worked out when a file is made, so they apply to files made after you add the filter. Changing Buyer reference on an order gives its documents new files, and keeps the earlier ones.

Emails and downloads

Filter	What it's for
folioline_email_documents	The documents attached to a WooCommerce email ($documents, $email_id, $order, $email).
folioline_can_download	Whether a user may download a document's files ($allowed, $document, $user_id). By default: staff who can edit orders or manage WooCommerce, and the order's own logged-in customer while My Account downloads are on.
folioline_admin_document_formats	The formats linked next to a document on the admin screens ($formats, $document). Default: pdf and the e-invoice format chosen for emails, or xrechnung-cii.

Admin screens and reports

Filter	What it's for
folioline_settings_fields	The fields on WooCommerce → Folioline ($fields). A field's key must be one Folioline's settings keep.
folioline_documents_tabs	The tabs on WooCommerce → Invoices ($tabs, tab => label). Print yours on folioline_documents_tab.
folioline_documents_columns	The columns of the Invoices list ($columns). Print yours on folioline_documents_column.
folioline_register_row	A row of the one-row-per-document register ($row, $document).
folioline_oss_rows	The OSS report's rows ($rows, $from, $to): country, rate, net, tax in euros.
folioline_csv_delimiter	The CSV separator ($delimiter): , by default, or ;, a tab or `

// Semicolon-separated CSV files for Excel in Germany, France or Italy.
add_filter( 'folioline_csv_delimiter', function () {
	return ';';
} );

Templates

Copy a template into your theme to change it, as for WooCommerce's own templates:

Template	Copy to
templates/document.php: the invoice and credit note PDF. It gets $document (the snapshot) and $view (formatting helpers). Print only what's in $document, never the order, so the PDF reads the same whenever it's made.	your-theme/folioline/document.php
templates/myaccount/documents.php: the Documents table in My Account.	your-theme/folioline/myaccount/documents.php

The PDF's styles are in assets/css/document.css (filter folioline_pdf_css).

Functions

Extendiment\Folioline\Documents reads and issues documents: get( $id ), invoice_for( $order_id ), credit_note_for( $order_id, $refund_id ), for_order( $order_id ), query( $args ), issue_invoice( $order ) and issue_credit_note( $order, $refund ). The issue methods return the existing document when there is one, so they're safe to call twice. Extendiment\Folioline\Output\Files::pdf( $document ) and ::xml( $document, $format ) return a stored file's path (or a WP_Error saying why it can't be made).

WP-CLI

Command
wp folioline issue <order>...	Issues each order's invoice, and credit notes for its refunds, if it has no invoice yet.
wp folioline list [--type=<type>] [--from=<Y-m-d>] [--to=<Y-m-d>] [--format=<table|csv|json>]	Lists documents. --type is invoice or credit_note.
wp folioline render <document>... [--format=<format>]	Prints a document's stored file path, making it first if needed. --format: pdf (default), zugferd, xrechnung-cii, xrechnung-ubl or peppol.