CI 3.1.5 php Warning shell_exec

in system CI checks if su_exec can be used. You should not see an error.
The error message tell you the problem is in you model file. Not in system/libary/upload.php.

Filename: models/Magazine_model.php
Line Number: 82

I doubt very much that the upload.php is your problem.

Thank you, this is line 82

PHP Code:

$this->db->order_by(`views`, 'asc');