Description:
------------
When accessing an array element with a string index which forms a 
number, it is inevitably converted to an integer.

Reproduce code:
---------------
<?php

$a = array();
$b = '1234';

$a['x'] = 'whatever';
$a[$b] = 'whatever2';

foreach ($a as $key=>$value) {
echo gettype($key)."\n";
}

?>


Expected result:
----------------
string
string

Actual result:
--------------
string
integer