Display a 'modal popup' anywhere in the system

Hi, and welcome to CodeIgniter! You cannot do that with PHP, so CodeIgniter cannot do it either. This is because of the client-server nature of PHP. Running on the server, PHP executes your script and sends the results to your browser, which is the client. At that point, PHP is no longer in control. It has no idea what keys you're pressing or what you're typing, so it can't do modal popups. For that, you need something that is running on the client, and that would be Javascript.

Now, you say suppose you're performing a client registration and remember another task you must do. Is that task unrelated to the client registration? For example, you are registering client A and suddenly remember you must bill $50 to client B immediately because they are about to print billing invoices? If that is the case, you can just open a second window or tab. Each window and tab operates independently of the other.

Hey, don't work without a PHP debugger. Several free IDEs have this features built in. Two are NetBeans and CodeLobster. Without a debugger, it's like you're driving with a blindfold on -- you are going to crash!