[Dovecot] PHP implementation of dovecotpw passwords

I am looking for PHP functions that implement passwords that much the dovecotpw implementation.

I downloaded one from PEAR, Crypt_HMAC, but the passwords it generates look nothing like the dovecotpw passwords, which could be my fault because I know nothing about the field.

Is there a guide or some library that implements them to match dovecotpw?