Cannot modify header information

[eluser]Armchair Samurai[/eluser]
Berserk has an excellent point - if you've encoded in UTF-8, there might be the invisible BOM mark at the beginning of your files which needs to be removed (easy enough, depending on your text editor) otherwise you will get the "Cannot modify header information" error.

Also, unrelated to the problem at hand, you've failed to load the model admin_model in your controller function verify where you actually need to access it, as opposed to index where it's loaded but not used.