Description:
------------
When implementing ArrayAccess, I was expecting to be able to preserve the original type of keys before they are used inside of an `array()` instance.

In PHP 7.2.17, string keys (and only keys of this type) are being cast down to integers, if they meet the qualifications explained in the array documentation (https://www.php.net/manual/en/language.types.array.php).

This seems like inconsistent behavior that should not be evaluated until a string is used on an instance of an `array()`.



Test script:
---------------
<?php

class A implements ArrayAccess
{
    public $accessedKeys = [];
    
    public function offsetGet($key)
    {
        array_push($this->accessedKeys, $key);
    }
    
    public function offsetExists($key)
    {
        throw new BadMethodCallException();
    }
    
    public function offsetSet($key, $value)
    {
        throw new BadMethodCallException();
    }
    
    public function offsetUnset($key)
    {
        throw new BadMethodCallException();
    }
}

$test = new A();
$test[1];
$test["1"];
$test["01"];
$test[1.0];
$test[true];

var_dump($test->accessedKeys);

Expected result:
----------------
I expect array key casting not to happen until a key is accessed or stored on an `array()` instance.

I would expect the above output to be:

array(5) {
  [0]=>
  int(1)
  [1]=>
  string(1) "1"
  [2]=>
  string(2) "01"
  [3]=>
  float(1)
  [4]=>
  bool(true)
}

Actual result:
--------------
Instead, the string key (and only the string key) is converted when used via ArrayAccess methods.

The above output actually is:

array(5) {
  [0]=>
  int(1)
  [1]=>
  int(1)
  [2]=>
  string(2) "01"
  [3]=>
  float(1)
  [4]=>
  bool(true)
}