Codeigniter image_thumb() stops execution

Question

I am using CodeIgniter 2.2.0 , apache 2.4.17, PHP 5.6.16.

When I need the thumbnail of any image I use the image_thumb() function.

But when I upload the image which has size more than 3 MB and then tries to get the thumbnail at that time execution is terminated without any error(error_reporting is ON).

I trace it and found resize()function called inside the image_thumb() function that is terminating execution.

So is it any Server issue?