Description:
------------
https://3v4l.org/T9HLm

Note that with PHP5, no "undefined variable offset" is emitted. I believe this is a BC break in PHP7.0. Also, I found this page: https://wiki.php.net/rfc/uniform_variable_syntax, which explicitly mentions: "E.g. empty([]['a']) will no longer throw an undefined offset notice."

This is seen with php-zeta-console-tools tests, and leads to a test failure.

Test script:
---------------
<?php
error_reporting(-1);

class obj implements ArrayAccess {
    private $container = array();

    public function __construct() {
        $this->container = array(
            "one"   => 1,
            "two"   => 2,
            "three" => 3,
        );
    }

    public function offsetSet($offset, $value) {
        if (is_null($offset)) {
            $this->container[] = $value;
        } else {
            $this->container[$offset] = $value;
        }
    }

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

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

    public function offsetGet($offset) {
        return isset($this->container[$offset]) ? $this->container[$offset] : null;
    }
}

$obj = new obj;
$obj[][0] = 'Append';

Expected result:
----------------
No notice to be emitted.

Actual result:
--------------
Notice: Undefined variable: offset in /in/T9HLm on line 32