When considering the chmod -R command, you may actually be wanting to descend, from some directory into all of its subdirectories to set the file permissions for a particular type of file. Directories should be 755, of course.
$ find . -type f -print $ find . -type f -name *.php -print
#1 will search the present working directory (.) for documents of type file (f) and print onto the standard output.
#2 will search the present working directory (.) for documents of type file (f), with filename ending with “.php” and print onto the standard output.
When you are satisfied that your find command is correct, add the xargs parameter to the end:
$ find -type f -print | xargs chmod 644
This will set file permissions in ALL subdirectories to be 644 or -rw-r–r–.