Auto send customer invoice when pending payment

AUTO SEND INVOICE WHEN STATUS CHANGED TO “PAYMENT PENDING”

Is there an easy way or any php code I can add to automate sending the customer invoice/order details when status is changed to “pending payment”?

I’m new to PHP, so if you can help and provide the code, that would be very helpful.

Currently, the store owner has to go into the order and manually select “send invoice” from the drop down. This is a step that I worry will be forgotten and it has the payment link in that email notification. If there is a way to trigger the invoice email automatically when order status is changed to “payment pending”, it would solve the issue.

Thank you