To change all the directories to 755 (drwxr-xr-x):
-> find /opt/lampp/htdocs -type d -exec chmod 755 {} ;
-> find ../root -type d -exec chmod 755 {} ;
// Where ../root AND /opt/lampp/htdocs
is the folder where the files exist
To change all the files to 644 (-rw-r--r--):
find /opt/lampp/htdocs -type f -exec chmod 644 {} ;