Code for display currencies at the time the order was placed no longer works

Hi,

I am getting the following error after upgrading the php to 8.1 and updating wordpress.

Fatal error: Cannot access offset of type string on string
/public_html/wp-content/themes/sisleystudio/woocommerce/pdf/sisleystudio/invoice.php (220)

This is due to few lines I used, sent by you few months ago.
I am going to send them in a separate message.

Regards,
Valentin