Description:
------------
mkdir() wont work properly when its parameter is a numeric string

Reproduce code:
---------------
<?php
$path = array('1/0/0001', '1/1/0001');
$cwd = getcwd();
foreach ($path as $p)
{
	$p = explode('/', $p);
	foreach ($p as $dir_name)
	{
		if (! is_dir("./$dir_name"))
		{
			mkdir("./$dir_name");
		}
		chdir("./$dir_name");
	}
	chdir($cwd);
}
?>


Expected result:
----------------
It should create two directory trees under current dir:
   1/0/0001
   1/1/0001




Actual result:
--------------
and the result is:
   1/0/0001    (correct)
   1/0001      (should be '1/1/0001')