What will be if ur models extends MY_Controller?

Don't waste your time trying to understand why it doesn't work and just fix your code. A model is not supposed to extend a controller. Also, I doubt the segmentation fault error is caused by your code. Because this error means PHP has crashed. It may be a bug in PHP itself or something is wrong with your server.

Sure u right. I just post this message for peoples, that like me have a bad luck.