Description:
------------
bad working a __get method

Test script:
---------------

<?php
class C1 {
    protected $arr = array( 'e1' => array() );

    public function __get($propertyName) {
        if(isset($this->arr[$propertyName])) return $this->arr[$propertyName];
    }

    public function __set($propertyName, $value) {
        if(isset($this->arr[$propertyName])) $this->arr[$propertyName] = $value;
    }
}

$c1 = new C1();

var_dump($c1->e1);

$c1->e1[] = 1;

var_dump($c1->e1);

Expected result:
----------------
array
  empty

 array
  0 => int 1

Actual result:
--------------
array
  empty

( ! ) Notice: Indirect modification of overloaded property C1::$e1 has no effect 
in E:\Server\xampp\htdocs\test.php on line 18

 array
  empty

Description:
------------
bad working a __get method

Test script:
---------------

<?php
class C1 {
    protected $arr = array( 'e1' => array() );

    public function __get($propertyName) {
        if(isset($this->arr[$propertyName])) return $this->arr[$propertyName];
    }

    public function __set($propertyName, $value) {
        if(isset($this->arr[$propertyName])) $this->arr[$propertyName] = $value;
    }
}

$c1 = new C1();

var_dump($c1->e1);

$c1->e1[] = 1;

var_dump($c1->e1);

Expected result:
----------------
array
  empty

 array
  0 => int 1

Actual result:
--------------
array
  empty

( ! ) Notice: Indirect modification of overloaded property C1::$e1 has no effect 
in E:\Server\xampp\htdocs\test.php on line 18

 array
  empty

things returned by __get() are read only.

When you have

$c1->e1[] = 1;

It's really calling __get on e1 and then appending to the array the value 1. The 
latter can't happen since it's read only.