Permission tmp problem: Change of tmp directory I recently installed one new Drupal (7.32) on a server that doesn't belong to me. Since then, I have a permission problem, I can't edit CHMOD rights and when I try to add new content (with image(s)), I can't. Here's the mistake returned by Drupal:

Warning: move_uploaded_file(): open_basedir restriction in effect.
File(/home/tmp/php/phpBKRRLYL) is not within the allowed path(s): (/home/tmp/sessions/:/home/XXX/public_html/:/home/XXX/shared) in drupal_move_uploaded_file() (line 1639 of /home/XXX/www/public_html/YYY/drupal-7.32/includes/file.inc).

Warning: move_uploaded_file(): open_basedir restriction in effect.
File(/home/tmp/php/phpBKRRLYL) is not within the allowed path(s): (/home/tmp/sessions/:/home/XXX/public_html/:/home/XXX/shared) in drupal_move_uploaded_file() (line 1639 of /home/XXX/www/public_html/YYY/drupal-7.32/includes/file.inc).

Warning: move_uploaded_file(/home/tmp/php/phpBKRRLYL): failed to open stream:
Operation not permitted in drupal_move_uploaded_file() (line 1639 of /home/XXX/www/public_html/YYY/drupal-7.32/includes/file.inc).

Warning: move_uploaded_file():
Unable to move '/home/tmp/php/phpBKRRLYL' to '/home/XXX/www/public_html/YYY/drupal-7.32/sites/default/files/anime.jpg' in drupal_move_uploaded_file() (line 1639 of /home/XXX/www/public_html/YYY/drupal-7.32/includes/file.inc).


As we can see, Drupal apparently uses the server's tmp directory (in which I have no rights) and I would like it to use another tmp directory in "/home/XXX/www/public_html/YYY/drupal-7.32/" so that I can add/edit content properly.
How could I do this? By editing the "/includes/file.inc" file (if so, which line(s) shall I modify to do this?)? Something else?

NB: The system administrator is unavailable for an extended period so he can't change my rights for now. That's why it's important that I could change this tmp directory.
Thank you!
You can edit the relevant setting in Configuration > Media > File system > Temporary directory (/admin/config/media/file-system). 

You can choose any directory in your document root skipping the forward slash. I would recommend you to specify tmp. Take care of the permissions.