.htaccess redirect empty directories to index.php but it's showing function name instead of executing it

Solution 1:

Finally I have transfered the index.php file to root of the server and fixed this issue by adding index.php?$uri to my try_files and YeaP the .htaccess file wasn't working at all

But I have a question that if I want to have my index.php in a subdirectory what should I do ?

By the way the name of this type of configuration is Front Controller and you can search about it by this name

Thanks