PHPEnkoder

PHPEnkoder is a port of the excellent Hivelogic
Enkoder to PHP and, more specifically,
to WordPress. It is used to display text in a way that users can see
and bots can’t.

The encoding system is directly and unabashedly stolen from the
BSD-licensed source of Hivelogic Enkoder, which works by randomly
encoding a piece of text and sending to the browser self-evaluating
Javascript that will generate the original text. This works in two
ways: first, a bot must first have a fairly complete Javascript
implementation (in particular, it must have eval); second, the
decoding process can be made arbitrarily computationally
intensive. This is similar to the idea of charging computational
payments to send e-mail, only this is actually implemented.

By default, PHPEnkoder scrambles e-mails in plaintext and in mailto:
links. It additionally provides a shortcode for manual scrambling,
used like so: [enkode text="shown to non-JS browsers"]this will be
scrambled[/enkode].