I have a database class which contains the following method:

class Database {

      // Fetch array - one column
    public function fetch_array_column_ex(){

        $query = $this->execute();

        return $query->fetchAll(PDO::FETCH_COLUMN, 0);

    } // End fetch_array() function


I then extended the Database class like so:

class Node extends Database {
     public function fetch_array_column_user($user_id) {
        $STH = $this->connection->prepare("SELECT username FROM user WHERE id = :user_id" );
        $STH->bindParam(':user_id', $user_id, PDO::PARAM_INT);
        return $STH;
}// End function fetch_array_column_user()
Instead of retuning $STH I want to call the Database method fetch_array_column_ex() but I'm getting confused about how...