set chmod for directory/files

Recursively chmod only for directory
find . -type d -exec chmod 755 {} \;
Recursively setting chmod on every directory for execting
chmod -R a+X *
Above +X flag is used to set execute bit for directories only.
Recursively chmod setting only for files.
find . -type f -exec chmod 644 {} \;
Recursively set chmod only for PHP files which have extensions (.php)
find . -type f -name '*.php' -exec chmod 644 {} \;