PHP classes and functions/ undefined variable - php

Question

Why do I get undefined property Takeover::user2 on function takeover?
I'm not sure what I'm doing wrong. Can someone help?
I can call user2->addsaldo() on main file but I can't call it inside another function. Why?
Class user
class User {
/**
* #AttributeType int
*/
private $iduser;
/**
* #AttributeType float
*/
private $saldo=0;
/**
* #AssociationType Portefolio
* #AssociationKind Composition
*/
public $idportefolio;
public function __construct($iduser){
$this->iduser = $iduser;
}
/**
* #access public
*/
public function getid() {
// Not yet implemented
}
/**
* #access public
*/
public function addsaldo($saldo) {
$this->saldo = $saldo;
}
}
Class takeover
class Takeover {
/**
* #AttributeType int
*/
private $idTakeover;
/**
* #AssociationType root
* #AssociationMultiplicity 1
*/
public $Root;
public $IdeasTakerover=array();
public function __construct($idTakeover){
$this->idTakeover = $idTakeover;
}
/**
* #access public
*/
public function GetIdCompraRoot() {
// Not yet implemented
}
public function AddIdeasTakeover($idTakeover, $idideia) {
$this->idTakeover = $idTakeover;
$this->idideia = $idideia;
array_push($this->IdeasTakerover,$idideia);
}
/**
* #access public
*/
public function Takeover() {
$this->user2->addsaldo(200); //USER2 DOES EXIST
}
}
Creating users and calling them:
$takeover = new Takeover(1);
for ($i=0; $i<$conta; $i++ ){
$takeover->AddIdeasTakeover(1,$idsideias[$i]);
}
$takeover->Takeover();
if ($partial == "user") {
$booleanUser = TRUE;
$iduser=substr($buffer, 4);
${'user'.$iduser} = new User($iduser);
}

Answer 1

The problem is not in this class. The problem is that $GLOBALS['user2'] is not defined when referenced here: $GLOBALS['user'.$this->IdeiasTakeover[$i]]. You then call addsaldo() on an undefined array element in $GLOBALS.
On another note, it is impossible to write good code using $GLOBALS. Global variables are bad news. You should not be using/referencing global variables. The exception would be at a low level when referencing $_POST, $_GET, etc. Even still, all the good PHP frameworks wrap these in a request object.
Edit
Dependency Injection is a better way for one class to use another:
class X {
$yInstance;
public function __construct($yInstance)
{
$this->yInstance = $yInstance;
}
public function x()
{
//Call your 'y' method on an instance of Y
$this->yInstance->y();
}
}
class Y {
public function y()
{
echo 'Y::y() called!';
}
}
Call X::x()
$y = new Y();
$x = new X($y);
$x->x();
Output:
Y::y() called!
The easiest way to do this is to use a dependency injection container. Here is my favorite one for PHP: http://symfony.com/doc/current/components/dependency_injection/introduction.html
Also, check out Martin Fowlers classic article about IOC:
http://martinfowler.com/articles/injection.html
Good luck!