email encryption Tiki plugin

<?php
/* Tiki-Wiki plugin EMENCR */
function wikiplugin_emencr($data, $params) {
    extract ($params,EXTR_SKIP);
    if (!isset($email)) { return ("<b>missing email address parameter for plugin</b><br />"); }
    $em = explode("@", $email);
    $ed = str_split($em[1], (strlen($em[1])/2)+1);
    $at = "'+\"&#\"+eval(60 + 4)"; # formula to create the number 64 for at sign
    $ret  = "{JS()}document.write('<' + 'a h' + 'ref=\"m'+'grailto:z'.substr(2,6)+'";
    $ret .= $em[0].$at."+';'+'" . $ed[0] . "'+'" . $ed[1];
    if ("$data" == "") {   # no data for link so make email address the link
         $ret .= "\">".$em[0].$at."+';'+'" . $ed[0] . "'+'" . $ed[1] . "</a>');{JS}";
    } else { # there is data so make it the link
         $ret .= "\">" . $data  . "</a>');{JS}";
    }
    return $ret;
}
?>