Why can't I use trim() in CodeIgniter 3.0?

Still doesn't work, I have no idea. But without using CI, trim() works. I give up solving this problem, because if the apache does not allow me to use almost all useful library and function of CI, this framework is useless in another word.  Thank you guys for all your help!

What version of Apache and PHP are you using? It really sounds like there's something else wrong here and you're just trying to work around a bigger issue that might be more easily fixed by taking it on directly.

Bonfire

Practical CodeIgniter 3
CodeIgniter Testing Guide