Invoicing Script

A free stand-alone script to handle invoicing and payment via PayPal smart checkout. Requires a free PayPal account and API key. Use this as a base to develop whatever is desired.

It is most basic

• The UI is not aesthectically dramatic, but can be formatted as desired
• The form fields has no labels, just placeholder attribute
• Data is saved as .json files
• Uses a simple login for administration. Can be developed for greater security if needed. The default password is admin_config and is stored in the file named admin. This file can be viewed via a browser so it should be protected. I use .htaccess but each server OS that's not Apache will have its own method to restrict file view.
• Form fields are not sanitized. Add security processes as needed
• If the MailJet SMTP tool will be used, the file named vendor.zip must be extracted to enable the dependent libraries. Requires a free account with mailjet.com. There is the standard mail() method available, however big bad gmail tends to return if DKIM and SPF does not match their requirements. Mailjet and other SMTP providers will deliver.
• Function names in functions.php are very common keywords and may cause conflict if loaded in WordPress or other packages. Either wrap within a class or make the names unique.

paths

• config - invoicing/?do_config=1
• create invoice - invoicing/?do_invoice=1
• edit an invoice - invoicing/?do_invoice=1&edit=invoice-3504.json
• view invoice - invoicing/?client=invoice-3504

Front Invoice View

Pay Via PayPal Smart Checkout Without Leaving Page

If there is no invoice, can serve as a pay resource

Invoice Creation

Configuration