Will recursively find all files inside current directory and call for these files dos2unix command. Would break if you had spaces in file name.
find . -type f -exec dos2unix {} \;
Wouldn't break if you had spaces in file names.
find . -type f -print0 | xargs -0 dos2unix
Convert only *.php files
find . -type f -name "*.php" -print0 | xargs -0 dos2unix
If it's a large directory you may want to consider running with multiple processors:
find . -type f -print0 | xargs -0 -n 1 -P 4 dos2unix
This will pass 1 file at a time, and use 4 processors.