This is my own class for private messaging system, built using plain PHP.
It's still under development. To find out more, visit the issues page.
The main core of this project is completed.
You can implement this on your website without any problems and use it.
Send a new message - send_message()
Respond to a message - send_message($respond > 0)
Get the list of all messages for a single user ( inbox ) - get_all_messages()
Get the number of unread messages - get_number_of_unread_messages()
Delete a single message or entire conversation - delete_message()
Notify user by email of new message - just uncomment the line 43
Best regards,
Igor Ilic