Parent的类构造函数调用错误？

I'm trying to call parent class constructor but it throws an error

Fatal error: Cannot call constructor

and the same code was working well before, I didn't change anything and but suddenly don't know what could have happened, It is throwing this error.

I've read some answers on stackoverflow, but they say that your parent class doesn't contain a constructor, well, this is not my case I have constructor in my parent class. Here's my code:

class DB
{
    var $con;

    public function __construct()
    {
        require_once 'configs/dbconfig.php';
        $this->connect();
    }

    function connect()
    {
        try{
            $this->con = new PDO('mysql:host='.DB_HOST.';dbname='.DB_NAME,DB_USER,DB_PASS);
            $this->con->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
        }catch(PDOException $ex) {
            echo $ex->getMessage();
        }
    }
}

and then I have a class Posts which is extending DB and calling DB's constructor.

class Posts extends DB
{
    var $user_id;

    public function __construct($user_id)
    {
        parent::__construct();
        $this->user_id = $user_id;
    }

    function get_posts($search,$pages,$since_id=0,$max_id=false,$count=20,$status='active')
    {
        $extra = '';
        if($search) $extra .= " AND text LIKE CONCAT('%',:search,'%')";
        if(!empty($pages)) $extra .= " AND page IN('".implode("','", $pages)."')";
        if(!empty($status) && $status != 'all') $extra .= " AND status=:status";

        $max_id = ($max_id) ? $max_id : time();

        $sqlCommand = "SELECT id,pid,text,media,media_url,type,name,u_id,username,user_profile_url,user_photo_url,post_url,date,status,source,page_id FROM ".POSTS." WHERE date>=:since_id AND date<=:max_id".$extra." AND user_id=:user_id ORDER BY date DESC LIMIT $count";
        $params = array(':since_id'=>$since_id,':max_id'=>$max_id,':user_id'=>$this->user_id);
        if($search) $params[':search'] = $search;
        if($status && $status != 'all') $params[':status'] = $status;

        $posts = $this->fetch($sqlCommand,$params);
        return $posts;
    }
}