Description:
------------
yeah, i know using "$obj->arr[]" with __set/__get, the result is undefined. but shouldn't it be denied? because it's causing really bad side effect now... and hard to debug if there's no warning.
it's hard to know the instance $obj will be used as $obj->arr[] = ''; else where, if the project is big enough, while u implement __set/__get for classes happily

relatived bug:
http://bugs.php.net/bug.php?id=33941

Reproduce code:
---------------
<?php
class test {
    private $vars;

    public function __construct($vars) {
        $this->vars = $vars;
    }

    public function __get($key)
    {
        echo "get $key\n";
        return $this->vars[$key];
    }

    public function __set($key, $value)
    {
        echo "set $key to $value \n";
        $this->vars[$key] = $value;
    }
}
$vars = array('test' => array(0 => ""));
$obj = new test($vars);
$obj->test[0] = 'modified';
var_dump($vars);
?>

to reproduce the leak in http://bugs.php.net/bug.php?id=33941
<?php
class test {
    private $vars;

    public function __construct($vars) {
        $this->vars = $vars;
    }

    public function __get($key)
    {
        return $this->vars[$key];
    }
}
$vars = array('test' => array(0 => ""));
$obj = new test($vars); 
$obj->undefined[0] = 'modified';
?>

Notice: Undefined index:  undefined in /tmp/test.php on line 12
[Wed Mar  1 19:08:25 2006]  Script:  './/test.php'
/usr/src/php5/Zend/zend_variables.h(45) :  Freeing 0x08765E2C (9 bytes), script=.//test.php
/usr/src/php5/Zend/zend_variables.c(120) : Actual location (location was relayed)
[Wed Mar  1 19:08:25 2006]  Script:  './/test.php'
/usr/src/php5/Zend/zend_execute.c(1020) :  Freeing 0x0877BACC (35 bytes), script=.//test.php
/usr/src/php5/Zend/zend_hash.c(383) : Actual location (location was relayed)
[Wed Mar  1 19:08:25 2006]  Script:  './/test.php'
/usr/src/php5/Zend/zend_execute.c(1076) :  Freeing 0x0877BA7C (32 bytes), script=.//test.php
/usr/src/php5/Zend/zend_hash.c(169) : Actual location (location was relayed)
Last leak repeated 1 time
[Wed Mar  1 19:08:25 2006]  Script:  './/test.php'
/usr/src/php5/Zend/zend_execute.c(842) :  Freeing 0x0877B9DC (16 bytes), script=.//test.php
[Wed Mar  1 19:08:25 2006]  Script:  './/test.php'
/usr/src/php5/Zend/zend_execute.c(1072) :  Freeing 0x0877B88C (16 bytes), script=.//test.php

Expected result:
----------------
output
array(1) {
  ["test"]=>
  array(1) {
    [0]=>
    string(0) ""
  }
}
and just don't call __get/__set, raising a warning


Actual result:
--------------
get test
array(1) {
  ["test"]=>
  array(1) {
    [0]=>
    string(8) "modified"
  }
}