SSL (Secure Socket Layer) is a protocol for transmitting private documents via the internet. It is not a program or a language. It works by using a public key to encrypt data that is transferred over the SSL connection.
It is basically a secure version of http, but SSL URLs start with "https" instead of "http".
You can either purchase your own authentication certificate or your host may allow you to share theirs. You should have no problems using PHP with SSL.
