Description:
------------
When integer used as object's property name, conversion to array by (array) makes normally integer array keys as string. In result, isset() and array_key_exists() doesn't work on malformed array.

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

# available on http://3v4l.org/ambbi

class ArrayHash extends \stdClass
{
	public static function from(array $arr)
	{
		$obj = new static;
		foreach ($arr as $key => $value) {
			$obj->$key = $value;
		}
		return $obj;
	}
}

$one = array('abcdef' => 'xxx', '102787' => 'yyy');
$two = (array) ArrayHash::from($one);


echo "# One\n";
var_dump($one);
var_dump(isset($one['abcdef']));
var_dump(array_key_exists('abcdef', $one));
var_dump(isset($one[102787]));
var_dump(array_key_exists(102787, $one));
var_dump(isset($one['102787']));
var_dump(array_key_exists('102787', $one));
echo "\n\n";


echo "# Two\n";
var_dump($two);
var_dump(isset($two['abcdef']));
var_dump(array_key_exists('abcdef', $two));
var_dump(isset($two[102787]));
var_dump(array_key_exists(102787, $two));
var_dump(isset($two['102787']));
var_dump(array_key_exists('102787', $two));
echo "\n\n";


Expected result:
----------------
# One
array(2) {
  ["abcdef"]=>
  string(3) "xxx"
  [102787]=>
  string(3) "yyy"
}
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)


# Two
array(2) {
  ["abcdef"]=>
  string(3) "xxx"
  ["102787"]=>
  string(3) "yyy"
}
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)


Actual result:
--------------
# One
array(2) {
  ["abcdef"]=>
  string(3) "xxx"
  [102787]=>
  string(3) "yyy"
}
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)


# Two
array(2) {
  ["abcdef"]=>
  string(3) "xxx"
  ["102787"]=>
  string(3) "yyy"
}
bool(true)
bool(true)
bool(false)
bool(false)
bool(false)
bool(false)