## Is tmpfile() restricted by open_basedir setting or not?

According to this comment on the PHP manual pages, the `tmpfile()` function is affected by the `open_basedir` setting.

Quoting from the mentioned comment about `tmpfile()`:
Remember, that open_basedir affects this function. You will get an error:

Warning: tmpfile() [function.tmpfile]: open_basedir restriction in effect. File(/var/tmp) is not within the allowed path(s): ....blablabla =)
Ok, I decided to test, so I altered my php.ini adding this restriction:

Code:
`open_basedir = D:\htdocs`
After restarting php, I checked with `phpinfo()` that the `open_basedir` was in effect, it was...

Fine, then lets try to run this script which should produce the mentioned warning message since my `TEMP` directory, `"C:\Windows\Temp"`, (as shown in `phpinfo()`) is now outside the `open_basedir`, and I would then not expect `tmpfile()` to be working.

PHP Code:
``` \$temp = tmpfile(); fwrite(\$temp, "writing to tempfile"); fseek(\$temp, 0); echo 'x:'.fread(\$temp, 1024); sleep(10); // sleep 10 seconds  ```
(According to the PHP documentation the temporary file created by `tmpfile()` will automatically be deleted again when the script ends so `sleep(10)` was added so I could check whether the temporary file was created or not while the script was running.)

Now comes the weird part... Strangely, I get absolutely no warning message when running the above script. On the contrary, `tmpfile()` seems to be totally unaffected by the `open_basedir` setting! And when I look in `"C:\Windows\Temp"` I indeed see the a file `phpX.tmp` appear and vanish when the script starts and stops. But `"C:\Windows\Temp"` is not within `"D:\htdocs"` which I has set as the `open_basedir` restriction and where the script is running.

My question is therefore: When is `tmpfile()` restricted by `open_basedir`, and when not?

Environment: PHP 5.2.6 / Apache / Microsoft Windows Server 2003

If it is of interest, the reason for the above question is that I am trying to figure out why some users are having trouble with the PEAR Spreadsheet_Excel_Writer on some hosts.