Good program to indent large quantity of files?

I haven't been indenting any of my code, but I want to start indenting to make the code more readable. It would be near-impossible for me to manually indent what's already there, though. So, I'm looking for a program to indent an entire folder of PHP files at once. Any suggestions? -- The above message is encrypted with double rot13 encoding. Any unauthorized attempt to decrypt it will be prosecuted to the full extent of the law.