Description:
------------
$array[] syntax does not work with ArrayAccess implementation.

Reproduce code:
---------------
<?php
class TestArray implements ArrayAccess {
    private $array = array();

    public function offsetExists($offset) {
        return isset($this->array[$offset]);
    }

    public function offsetGet($offset) {
        return $this->array[$offset];
    }

    public function offsetSet($offset, $value) {
        $this->array[$offset] = $value;
    }

    public function offsetUnset($offset) {
        unset($this->array[$offset]);
    }
}

$test = new TestArray;

// Does not work.
$test[] = 'Hello'; $test[] = ' World!';

// Works.
// $test[0] = 'Hello'; $test[1] = ' World!';

print $test[0] . $test[1];
?>

Expected result:
----------------
Hello World!

Actual result:
--------------
Notice: Undefined offset:  0 in D:\test2.php on line 10
Notice: Undefined offset:  1 in D:\test2.php on line 10