Event Hooks
There are a lot of event hooks built in to FOSSBilling that you can use to call events when needed.
They are listed below without further explanation, but the titles should make it pretty clear when each one will be run.
- onAfterAdminActivateExtension
 - onAfterAdminBatchSuspendOrders
 - onAfterAdminClientDelete
 - onAfterAdminClientPasswordChange
 - onAfterAdminClientUpdate
 - onAfterAdminCloseTicket
 - onAfterAdminCreateClient
 - onAfterAdminCronRun
 - onAfterAdminDeactivateExtension
 - onAfterAdminDeleteCurrency
 - onAfterAdminExtensionConfigSave
 - onAfterAdminGenerateRenewalInvoice
 - onAfterAdminInstallExtension
 - onAfterAdminInvoiceApprove
 - onAfterAdminInvoiceDelete
 - onAfterAdminInvoiceRefund
 - onAfterAdminInvoiceReminderSent
 - onAfterAdminInvoiceUpdate
 - onAfterAdminLogin
 - onAfterAdminNotificationAdd
 - onAfterAdminOpenTicket
 - onAfterAdminOrderActivate
 - onAfterAdminOrderCancel
 - onAfterAdminOrderCreate
 - onAfterAdminOrderDelete
 - onAfterAdminOrderDelete
 - onAfterAdminOrderRenew
 - onAfterAdminOrderSuspend
 - onAfterAdminOrderUncancel
 - onAfterAdminOrderUnsuspend
 - onAfterAdminOrderUpdate
 - onAfterAdminPublicTicketClose
 - onAfterAdminPublicTicketOpen
 - onAfterAdminPublicTicketReply
 - onAfterAdminReplyTicket
 - onAfterAdminSettingsUpdate
 - onAfterAdminStaffApiKeyChange
 - onAfterAdminStaffApiKeyChange
 - onAfterAdminStaffCreate
 - onAfterAdminStaffDelete
 - onAfterAdminStaffPasswordChange
 - onAfterAdminStaffProfilePasswordChange
 - onAfterAdminStaffProfilePasswordChange
 - onAfterAdminStaffProfileUpdate
 - onAfterAdminStaffProfileUpdate
 - onAfterAdminStaffUpdate
 - onAfterAdminSubscriptionCreate
 - onAfterAdminSubscriptionDelete
 - onAfterAdminTransactionCreate
 - onAfterAdminTransactionProcess
 - onAfterAdminTransactionUpdate
 - onAfterAdminUninstallExtension
 - onAfterClientCalledExampleModule
 - onAfterClientChangeNameservers
 - onAfterClientCloseTicket
 - onAfterClientLogin
 - onAfterClientOpenTicket
 - onAfterClientOrderCreate
 - onAfterClientProfilePasswordChange
 - onAfterClientProfilePasswordChange
 - onAfterClientProfileUpdate
 - onAfterClientProfileUpdate
 - onAfterClientReplyTicket
 - onAfterClientSignUp
 - onAfterGuestPublicTicketClose
 - onAfterGuestPublicTicketOpen
 - onAfterGuestPublicTicketReply
 - onAfterProductAddedToCart
 - onBeforeAdminActivateExtension
 - onBeforeAdminBatchSuspendOrders
 - onBeforeAdminClientDelete
 - onBeforeAdminClientPasswordChange
 - onBeforeAdminClientUpdate
 - onBeforeAdminCreateClient
 - onBeforeAdminCronRun
 - onBeforeAdminDeactivateExtension
 - onBeforeAdminDeleteCurrency
 - onBeforeAdminExtensionConfigSave
 - onBeforeAdminGenerateRenewalInvoice
 - onBeforeAdminInstallExtension
 - onBeforeAdminInvoiceApprove
 - onBeforeAdminInvoiceDelete
 - onBeforeAdminInvoiceRefund
 - onBeforeAdminInvoiceSendReminder
 - onBeforeAdminInvoiceSendReminders
 - onBeforeAdminInvoiceUpdate
 - onBeforeAdminLogin
 - onBeforeAdminOpenTicket
 - onBeforeAdminOrderActivate
 - onBeforeAdminOrderActivate
 - onBeforeAdminOrderActivate
 - onBeforeAdminOrderCancel
 - onBeforeAdminOrderCreate
 - onBeforeAdminOrderDelete
 - onBeforeAdminOrderDelete
 - onBeforeAdminOrderRenew
 - onBeforeAdminOrderSuspend
 - onBeforeAdminOrderUncancel
 - onBeforeAdminOrderUnsuspend
 - onBeforeAdminOrderUpdate
 - onBeforeAdminPublicTicketOpen
 - onBeforeAdminSettingsUpdate
 - onBeforeAdminStaffApiKeyChange
 - onBeforeAdminStaffApiKeyChange
 - onBeforeAdminStaffCreate
 - onBeforeAdminStaffDelete
 - onBeforeAdminStaffPasswordChange
 - onBeforeAdminStaffProfilePasswordChange
 - onBeforeAdminStaffProfilePasswordChange
 - onBeforeAdminStaffProfileUpdate
 - onBeforeAdminStaffProfileUpdate
 - onBeforeAdminStaffUpdate
 - onBeforeAdminTransactionCreate
 - onBeforeAdminTransactionProcess
 - onBeforeAdminTransactionUpdate
 - onBeforeAdminUninstallExtension
 - onBeforeClientChangeNameservers
 - onBeforeClientCheckout
 - onBeforeClientInvoiceDelete
 - onBeforeClientLogin
 - onBeforeClientOpenTicket
 - onBeforeClientProfilePasswordChange
 - onBeforeClientProfilePasswordChange
 - onBeforeClientProfileUpdate
 - onBeforeClientProfileUpdate
 - onBeforeClientSignUp
 - onBeforeGuestPasswordResetRequest
 - onBeforeGuestPublicTicketOpen
 - onBeforeProductAddedToCart
 - onEventAdminLoginFailed
 - onEventAfterInvoiceIsDue
 - onEventBeforeInvoiceIsDue
 - onEventClientLoginFailed
 - onBeforeAdminUpdateCore
 - onAfterAdminUpdateCore
 - onBeforeAdminUpdateExtension
 - onAfterAdminUpdateExtension
 - onBeforeAdminClientCreate
 - onAfterAdminClientCreate