WHMCS may return PHP errors and exceptions if errors occur.
You can view information about your PHP configuration from within the Admin Area.
To meet WHMCS's PHP version requirements, you may need to periodically update PHP to a new supported version.
You can check your system's compatibility with PHP from within the Admin Area.
Promotions add discounts to your items for sale. You can configure many types of discount, set up free trials, and create promotion codes.
How to troubleshoot question marks replacing text in PDF invoices and quotes.
Quotes allow you to send estimates to customers. If the customer accepts your quote, you can easily convert the quote into an invoice.