Submiting UTF-8 XML via POST

Hi,

I'm having a problem with encodings and form submission using PHP.

(All my scripts are in UTF-8 with the correct declaration in the HTML
header.)

* I have a XML document in UTF-8.
* Using GET edit.php, I read the file (using file_get_contents) and
present it in a textarea within a HTML form.
* When the form is submited with POST edit.php, I store it in the same
file.

The problem is: even without any editing (just submit), the data in
the file gets corrupted. Only a few characters are stored wrongly. I
still haven't figured out what characters are causing the problem but
"//////" symbols are added to it.

I'am not using any of the utf8_(dec)encode functions.

Any help would be greatly appreciated.

Thanks in advance,
Sérgio Nunes