This is very useful to prevent spam robots collecting email addresses from your site, included is a method to add mailto links to the text being generated.
The "encryption" function is basically works like ROT13, with the difference that the $offset setting replaces the 13. It is also limited to ASCII characters between 32 and 127 (included). Other characters will not be encrypted.
a basic example to encrypt an email address $c = new HTML_Crypt('firstname.lastname@example.org', 8); $c->addMailTo(); $c->output();