<?php


class MyClass
{
    public $stdObj;
    public function __construct()
    {
        $this->stdObj = new stdClass();
    }
}

$myObj = new MyClass();
var_dump($myObj->stdObj);

class MyClass2
{
    public $pdoObj;
    public function __construct()
    {
        $this->pdoObj = new PDO("mysql:host=localhost;dbname=test", "root", "");
    }
}

$myObj2 = new MyClass2();
var_dump($myObj2->pdoObj);