Why can't I do this in CI?

[eluser]Aken[/eluser]
I did notice that the redirect is commented out, but you also have comments describing the problem right above it, so I'm addressing that.

My guess is the set_session() method is working just fine. Try making the property public, and then var_dump it in your controller after setting it.

The problem is, all your set_session() method is doing is assigning a value to a property. Once you make another page request, via refresh or redirect, that property is gone, because your class has been newly instantiated. Upon that new instantiation, the __construct() function is then using the _session_id property, which is NULL, because nothing has changed it yet in that request.