Description:
------------
When using objects it can become very ambiguous what is occuring once you start using variable variable names.  The reproduce code shows a non-useful example of where this might occur.

A concise example of the problem:
$ob->field[0]  ==> array[0] ==> item
$ob->$field[0] ==> $ob->'b' ==> array

Being able to use brackets or something similar to force the -> operator to act before the [] would allow for a choice of functionality in the second example and provide the ability to make the code clearer.

$ob->($field[0]) 
($ob->$field)[0]

Both of these examples are currently not possible, a syntax error, unexpected ( or [ occurs.

Reproduce code:
---------------
<?php
class Arrayise {
    function __get($name) {
        return array($name);
    }
}

$ob = new Arrayise;
$field = 'bar';
var_dump($ob->$field[0]); // b
var_dump($ob->field[0]);  // bar
?>