public function make_url_clickable_cb($matches) {
$ret = '';
$url = $matches[2];

if ( empty($url) )
    return $matches[0];
// removed trailing [.,;:] from URL
if ( in_array(substr($url,-1),array('.',',';',':')) === true ) {
    $ret = substr($url,-1);
    $url = substr($url,strlen($url)-1);
}
return $matches[1] . "<a href=\"$url\" rel=\"nofollow\">" . $this->truncate($url,35,'...'). "</a>" . $ret;
}

public function make_web_ftp_clickable_cb($matches) {
    $ret = '';
    $dest = $matches[2];
    $dest = 'http://' . $dest;

    if ( empty($dest) )
        return $matches[0];
    // removed trailing [,;:] from URL
    if ( in_array(substr($dest,':')) === true ) {
        $ret = substr($dest,-1);
        $dest = substr($dest,strlen($dest)-1);
    }
    return $matches[1] . "<a href=\"$dest\" rel=\"nofollow\">$dest</a>" . $ret;
}

public function make_email_clickable_cb($matches) {
    $email = $matches[2] . '@' . $matches[3];
    return $matches[1] . "<a href=\"mailto:$email\">$email</a>";
}
public function make_clickable($ret) {
    $ret = ' ' . $ret;
    // in testing,using arrays here was found to be faster
    $ret = preg_replace_callback('#([\s>])([\w]+?://[\w\\x80-\\xff\#$%&~/.\-;:=,?@\[\]+]*)#is','Main::make_url_clickable_cb',$ret);
    $ret = preg_replace_callback('#([\s>])((www|ftp)\.[\w\\x80-\\xff\#$%&~/.\-;:=,'Main::make_web_ftp_clickable_cb',$ret);
    $ret = preg_replace_callback('#([\s>])([.0-9a-z_+-]+)@(([0-9a-z-]+\.)+[0-9a-z]{2,})#i','Main::make_email_clickable_cb',$ret);

    // this one is not in an array because we need it to run last,for cleanup of accidental links within links
    $ret = preg_replace("#(<a( [^>]+?>|>))<a [^>]+?>([^>]+?)</a></a>#i","$1$3</a>",$ret);
    $ret = trim($ret);
    return $ret;
}

为什么这不起作用？
我收到这些错误：

警告：preg_replace_callback()[function.preg-replace-callback]：需要参数2,’Main :: make_url_clickable_cb’,才能成为第134行的有效回调

警告：preg_replace_callback()[function.preg-replace-callback]：需要参数2,’Main :: make_web_ftp_clickable_cb’,才能成为第135行的有效回调

警告：preg_replace_callback()[function.preg-replace-callback]：需要参数2,’Main :: make_email_clickable_cb’,才能成为第136行的有效回调