encryption helper for php provides functions to encrypt, decrypt, and 
sign data using gpg or pgp commands.

encrypt_command, sends data to encrypt to stdin, returns result code
encrypt_command expects a gpg command like
/usr/bin/gpg --homedir /home/www-data/.gnupg --armor --batch -e -r 'USERNAME'

decrypt_command, sends passphrase to stdin, returns decrypted data
decrypt_command expects a gpg command like:
/usr/bin/gpg --homedir /home/www-data/.gnupg --passphrase-fd 0 --yes --no-tty --skip-verify --decrypt file.gpg
 
sign_command, sends passphrase to stdin for a file signature, returns nothing on success
sign_command expects a gpg command like:
/usr/bin/gpg --homedir /home/www-data/.gnupg --passphrase-fd 0 --yes --no-tty --clearsign file.tmp