[BUG] Fatal error in Admin.php – Call to get_prefix() on string (PHP 8.1)

Resolved lurim
(@lurim)

4 months, 1 week ago
Hello,

I’m experiencing a fatal error in the WooCommerce admin order screen when using PDF Invoices & Packing Slips for WooCommerce. Environment
- WordPress: 6.9
- WooCommerce: current (latest stable)
- Plugin: PDF Invoices & Packing Slips for WooCommerce 5.6.0
- PHP: 8.1
- Hosting: All-Inkl
Description

The shop frontend works perfectly:
- Orders are placed successfully
- Payments (Mollie) are completed
- Emails are sent
- PDF invoices are generated correctly
However, when opening an order in the WooCommerce backend, the metabox “PDF Document Data” shows a critical error and the admin page breaks partially. Error message

Fatal error: Uncaught Error: Call to a member function get_prefix() on string
in wp-content/plugins/woocommerce-pdf-invoices-packing-slips/includes/Admin.php:990

This seems to happen while loading the admin metabox.
Even disabling the metabox via hooks does not help, which suggests the error occurs during file load. Notes
- The issue also occurred with PHP 8.5 (worse), PHP 8.1 reduced it to backend-only
- Downgrading PHP is not preferred for security reasons
- Downgrading the plugin has not been tested yet
- This looks like a compatibility issue with PHP 8.x in the admin code
Question

Is this a known bug in version 5.6.0?
Is there a planned fix or recommended workaround (besides downgrading the plugin)?

Thanks for your work on the plugin and any guidance you can provide.

Best regards
- This topic was modified 4 months, 1 week ago by lurim.
- This topic was modified 4 months, 1 week ago by lurim.

Viewing 5 replies - 1 through 5 (of 5 total)

Plugin Contributor

Yordan Soares

(@yordansoares)

4 months ago

Hi @lurim,

Could you try updating the plugin up to the latest release, which currently is 5.7.0?

Let me know if it fixed the issue, or not!

Thread Starter

lurim

(@lurim)

3 months, 2 weeks ago

Hi Yordan, I hope you got my email. Just to be sure – the error isn’t fixed .
Do you have an idea when it’s solved – wordpress sends me daily an email with this content

Fehler-Details

==============

Ein Fehler vom Typ E_ERROR wurde in der Zeile 1018 der Datei /www/htdocs/w0204759/connywolf.com/wp-content/plugins/woocommerce-pdf-invoices-packing-slips/includes/Admin.php verursacht. Fehlermeldung: Uncaught Error: Call to a member function get_prefix() on string in /www/htdocs/w0204759/connywolf.com/wp-content/plugins/woocommerce-pdf-invoices-packing-slips/includes/Admin.php:1018

Stack trace:

#0 /www/htdocs/w0204759/connywolf.com/wp-content/plugins/woocommerce-pdf-invoices-packing-slips/includes/Admin.php(1152): WPO\IPS\Admin->get_current_values_for_document_data(Object(WPO\IPS\Documents\Invoice), Array)

#1 /www/htdocs/w0204759/connywolf.com/wp-content/plugins/woocommerce-pdf-invoices-packing-slips/includes/Admin.php(992): WPO\IPS\Admin->output_number_date_edit_fields(Object(WPO\IPS\Documents\Invoice), Array)

#2 /www/htdocs/w0204759/connywolf.com/wp-admin/includes/template.php(1453): WPO\IPS\Admin->data_input_box_content(Object(Automattic\WooCommerce\Admin\Overrides\Order), Array)

#3 /www/htdocs/w0204759/connywolf.com/wp-content/plugins/woocommerce/src/Internal/Admin/Orders/Edit.php(506): do_meta_boxes(Object(WP_Screen), 'normal', Object(Automattic\WooCommerce\Admin\Overrides\Order))

#4 /www/htdocs/w0204759/connywolf.com/wp-content/plugins/woocommerce/src/Internal/Admin/Orders/Edit.php(410): Automattic\WooCommerce\Internal\Admin\Orders\Edit->render_meta_boxes()

#5 /www/htdocs/w0204759/connywolf.com/wp-content/plugins/woocommerce/src/Internal/Admin/Orders/PageController.php(295): Automattic\WooCommerce\Internal\Admin\Orders\Edit->display()

#6 /www/htdocs/w0204759/connywolf.com/wp-includes/class-wp-hook.php(341): Automattic\WooCommerce\Internal\Admin\Orders\PageController->output('')

#7 /www/htdocs/w0204759/connywolf.com/wp-includes/class-wp-hook.php(365): WP_Hook->apply_filters('', Array)

#8 /www/htdocs/w0204759/connywolf.com/wp-includes/plugin.php(522): WP_Hook->do_action(Array)

#9 /www/htdocs/w0204759/connywolf.com/wp-admin/admin.php(264): do_action('woocommerce_pag...')

#10 {main}

  thrown

Plugin Contributor

Mohamad

(@mohamadntr)

3 months ago

Hi @lurim,

Could you please contact us through [email protected] so we can further investigate this issue?

Thread Starter

lurim

(@lurim)

3 months ago

Hi Mohamad,
I sent you an email just now

best regards

Lutz

Thread Starter

lurim

(@lurim)

3 months ago

@mohamad,
thank you for your advice. I made the change in the code of snippets and it works now fine.
Maybe somebody is interested

/**

PDF Invoices & Packing Slips: Erweiterte Platzhalter für Rechnungsnummern
[yy] = 2-stelliges Jahr (z. B. 25 für 2025)
[invoice_year] = 4-stellig (z. B. 2025)
[number] = fortlaufende Rechnungsnummer mit führenden Nullen
Fehlerfrei, auch wenn $document mal kein Objekt ist
/ /add_filter( ‘wpo_wcpdf_invoice_number’, function( $number, $type, $document ) { */
add_filter( ‘wpo_wcpdf_format_document_number’, function( $number, $type, $document ) { // 1. Standard-Jahr 4-stellig
$invoice_year = date_i18n(‘Y’); // Default
$yy = date_i18n(‘y’); // 2-stelliges Jahr Default // 2. Prüfen, ob $document ein Objekt ist
if ( is_object( $document ) && method_exists( $document, ‘get_date’ ) ) {
$date = $document->get_date();
if ( $date ) {
$invoice_year = date_i18n( ‘Y’, strtotime( $date ) );
$yy = date_i18n( ‘y’, strtotime( $date ) );
}
} // 3. Platzhalter ersetzen
$number = str_replace( ‘[invoice_year]’, $invoice_year, $number );
$number = str_replace( ‘[yy]’, $yy, $number ); // [number] bleibt unverändert (wird vom Plugin gesetzt)
return $number;

}, 10, 3 );

best regards
Lutz

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