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/**
 * Protect an email address from harvesting
 * based on http://www.maurits.vdschee.nl/php_hide_email/
 *
 * @param string $email email address to protect
 * @param string $text (optional) The text of the link.
 * @param string $extra (optional) Any extra parameters on the <a> tag
 * @param string $subject (optional) Subject of the email
 * @return string the link
 */
function hide_email($email,$text='',$extra='',$subject='') {
    $character_set = '+-.0123456789@ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz';
    $key = str_shuffle($character_set); $cipher_text = ''; $id = 'e'.rand(1,999999999);
    for ($i=0;$i<strlen($email);$i+=1) $cipher_text.= $key[strpos($character_set,$email[$i])]; $script = 'var a="'.$key.'";var b=a.split("").sort().join("");var c="'.$cipher_text.'";var d="";'; $script.= 'for(var e=0;e<c.length;e++)d+=b.charAt(a.indexOf(c.charAt(e)));'; $script.= 'document.getElementById("'.$id.'").innerHTML="<a href=\\"mailto:"+d+"?subject='.$subject.'\\" '.$extra.' >'.$text.'</a>"'; $script = "eval(\"".str_replace(array("\\",'"'),array("\\\\",'\"'), $script)."\")"; $script = '<script type="text/javascript">/*<![CDATA[*/'.$script.'/*]]>*/</script>'; return '<span id="'.$id.'">[javascript protected email address]</span>'.$script;
}

function shortcode_hide_email($atts)
{
    $a = shortcode_atts(array(
        'email' => '',
        'text' => $atts['email'],
        'extra' => '',
        'subject' => ''
    ), $atts);
    /** @var string $email */
    /** @var string $subject */
    /** @var string $extra */
    /** @var string $text */
    extract($a);
    if (!empty($subject)) {
        $subject = '?subject='.$subject;
    }
    $character_set = '+-.0123456789@ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz';
    $key = str_shuffle($character_set);
    $cipher_text = '';
    $id = 'e' . rand(1, 999999999);
    for ($i = 0; $i < strlen($email); $i += 1) $cipher_text .= $key[strpos($character_set, $email[$i])];
    $script = 'var a="' . $key . '";var b=a.split("").sort().join("");var c="' . $cipher_text . '";var d="";';
    $script .= 'for(var e=0;e<c.length;e++)d+=b.charAt(a.indexOf(c.charAt(e)));';

    $script .= 'document.getElementById("' . $id . '").innerHTML="<a href=\\"mailto:"+d+"' . $subject . '\\" ' . $extra . ' >' . $text . '</a>"';
    $script = "eval(\"" . str_replace(array("\\", '"'), array("\\\\", '\"'), $script) . "\")";
    $script = '<script type="text/javascript">/*<![CDATA[*/' . $script . '/*]]>*/</script>';
    return '<span id="' . $id . '">[javascript protected email address]</span>' . $script;
}

add_shortcode('hide_email', 'shortcode_hide_email');