Why mkdir fails with recursive option set true?

Question

I run the following code:

mkdir('mnt/1',0777,true);
mkdir('mnt/a',0777);

Directory "a" is created, while directory "1" is not, page prints warning.

Warning: mkdir(): File exists in /home/bitrix/www/php_test.php on line 3

I have full permissions on directory mnt for user apache is running:

drwxr-xr-x 1 bitrix bitrix   4096 Nov 28 10:10 mnt

PHP version - PHP 5.3.3. Apache version 2.2.15.

Any ideas, why mkdir fails with recursive option set to true?

Update! Well I cleared the folder, made the following php-script and ran it again:

<?php
        error_reporting(E_ALL);
        mkdir('mnt/1',0777,true);
        mkdir('mnt/2/',0777,true);
        mkdir('./mnt/3',0777,true);
        mkdir('./mnt/4/',0777,true);

        mkdir('mnt/a',0777);
        mkdir('mnt/b/',0777);
        mkdir('./mnt/c',0777);
        mkdir('./mnt/d/',0777);
?>

Here is the output:

Warning: mkdir(): File exists in /home/bitrix/www/php_test.php on line 3 
Warning: mkdir(): File exists in /home/bitrix/www/php_test.php on line 4 
Warning: mkdir(): File exists in /home/bitrix/www/php_test.php on line 5 
Warning: mkdir(): File exists in /home/bitrix/www/php_test.php on line 6

Here is the content of the folder mnt after script execution:

drwxr-xr-x  1 bitrix bitrix  4096 Nov 28  2012 .
drwxrwx--- 11 bitrix bitrix 12288 Nov 28 11:10 ..
drwxr-xr-x  1 bitrix bitrix     0 Nov 28  2012 a
drwxr-xr-x  1 bitrix bitrix     0 Nov 28  2012 b
drwxr-xr-x  1 bitrix bitrix     0 Nov 28  2012 c
drwxr-xr-x  1 bitrix bitrix     0 Nov 28  2012 d

I also tried absolute path for recursive mkdir - still no luck, while non-recursive mkdir works fine no matter how the path is set. What's wrong with recursive mkdir? I still have no ideas..

Update! Further investigation revealed that such things happen because mnt is a folder, mounted by command

mount -t cifs -o username=***user***,password=***password***,uid=bitrix,gid=bitrix,iocharset=utf8,codepage=866 //192.168.1.6/folder /home/bitrix/www/mnt

In all other directories recursive mkdir works fine, while in that directory only non-recursive mkdir works!

Update! As femtoRgon assumed mkdir, when run from script in the folder mnt, works fine both recursive and non-recursive. But still I can't figure out, why it fails, when run from /home/bitrix/www? I even tried mounting with options file_mode=0775,dir_mode=0775 - no luck. My OS = CentOS 6.3, if it matters..

Answer 1

After some googling, I found the answer on php.net. It is all about serverino mount option. When I mounted folder with noserverino all problems were gone. Anyway thanks guys for trying to help!