part of source of index.php visible

Look at your index.php file at the application and system folder paths ../../

That is wrong in CodeIgniter 3x it's application and system no ../../

Thats just part of your problem, check your paths and make sure there right.
.

Paths are valid.
I added +x permission to /home and /home/robert and now application praca runs.
But the problem still occurs in other 2 applications rozgloszenia1 and rozgloszenia2 - i.e. php source code is displayed.
Here structure of my applications:

~/public_html/praca
~/Projekty/praca/application

~/public_html/rozgloszenia1
~/Projekty/rozgloszenia1/application

~/public_html/rozgloszenia2
~/Projekty/rozgloszenia2/application

Permissions are the same for all applications.
What could be the reason of my problem?