Short wordpress URL /?p= in twitter button not showing URL in tweet

I like DigDig plugin but only thing what I would like to change is to have shorter URL in tweets(not some .ly shortner) but to use example.com/?p=123 instead of example.com/2013/../../… I did that on my autoposting tweets plugin it is working perfectly but I can not make it working on this plugin.

This code is constucting URL

public function constructURL($url, $title,$button, $postId, $globalcfg = ''){

    if($this->isEncodeRequired){
        $title = rawurlencode($title);
        $url = rawurlencode($url);
    }

    $twitter_source = '';
    if($globalcfg!=''){
        $twitter_source = $globalcfg[DD_GLOBAL_TWITTER_OPTION][DD_GLOBAL_TWITTER_OPTION_SOURCE]; 
    }


        //format twitter source
        $this->baseURL = str_replace(self::VOTE_SOURCE,$twitter_source,$this->baseURL);

        $this->constructNormalURL($url, $title,$button, $postId);

I want that URL to look like this $url = 'example.com/?p=' . $postId; But when I enter this code it is not showing any link.

This code is function of button in frontend

function dd_twitter_generate($buttonDesign=’Normal’, $source=”){
$post_data = dd_getPostData();

global $globalcfg;
$globalcfg[DD_GLOBAL_TWITTER_OPTION][DD_GLOBAL_TWITTER_OPTION_SOURCE] = $source;

$dd_twitter = new DD_Twitter();
$dd_twitter->constructURL($post_data['link'],$post_data['title'],$buttonDesign,$post_data['id'],false,$globalcfg);

echo $dd_twitter->finalURL;

}