Email Obfuscation Shortcode for WordPress

email_obfuscation.php

<?php
/*
Plugin Name: Email Obfuscation Shortcode
Plugin URI: https://gist.github.com/1424515
Description: Shortcode for including emails into content and keeping spambots clueless. [obf email="[email protected]" noscript="what's shown to bots/people without javascript"]
Version: 0.1
Author: Ismo Vuorinen
Author URI: http://github.com/ivuorinen 
*/

/**
 * emailobfusction_func
 *
 * @param   string $atts attributes
 * @return  string obfuscated email with javascript clarifying
 */
function emailobfusction_func( $atts )
{
	extract( shortcode_atts( array(
		'email'     => get_settings('admin_email'), // Defaulting to admin email
		'noscript'  => 'myname at thisdomain.com',
	), $atts ) );

    // JavaScript by Allan Odgaard
    // http://pastie.textmate.org/101495 (line 116)
    $javascript = '.replace(/[a-zA-Z]/g, function(c){ return String.fromCharCode((c<="Z"?90:122)>=(c=c.charCodeAt(0)+13)?c:c-26 );})';

    return '<script type="text/javascript">'
            . 'document.write("'
            . str_rot13( "<a class='rot13' href='mailto:" . $email . "'>" . $email . '</a>' )
            . '"' . $javascript . ');</script>'
            . '<noscript>' . $noscript . '</noscript>';
}
add_shortcode( 'obf', 'emailobfusction_func' );