If it only happens with IE, or one version of IE, then it's not a bug in PHP but yet another bug in IE.

this may be true, but do you know how this happens or how I can analyze the problem, because I don't get $HTTP_RAW_POST_DATA when enctype is set to "multipart/form-data", even when I set always_populate_raw_post_data = On.

My workarround for now is to put the select post results through array_unique (),

It happens because some guy at Microsoft was drunken.

Infact you are triggering a situation where the IE 5.0
simply sends every form field 2 times.

I could trace the same behaviour in a different script: IE5.0, multipart/formdata and a special char copied from a Winword document.

Indeed, I wonder, if it is IE5.0 that is doubling the array, or there is any strange thing (in IE5.0) that causes php to double the array when receiving it. The first is of course a bug in IE5.0. The latter would be one in php.

Maybe a developer can sniff the transmitted code and trace if IE5.0 is already doubling the value(s) or if this happens in php's value-handling.

Ren?
PS: For the time being we use array_unique() to filter out the doubled values in our array but this is not helpful if double values are allowed in an array.

Can you test 4.3.3RC1?  Many Apache2+PHP issues have been fixed since PHP 4.2.2.  Reporting bugs with PHP 4.2.2 is pretty much useless, despite what RH ships with.

Download 4.3.3 here:
http://qa.php.net/

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I believe it is Internet Explorer 5 and 6. I have seen this happen on Win2k, IIS and ASP.

What it looks like is that IE restarts building the formdata after a certain point, sometimes using the same boundary, sometimes using a different boundary. When it uses the same boundary, the formfields that have been already processed, will be repeated. When it uses another boundary, it depends on how the formdata are being parsed: if only the last boundary is being used (the one that is send along as a header), usually there are no problems, although sometimes the first formfield is send corrupted (and missing after parsing).

I have seen the behaviour both in IE 5 and 6, although IE 6 seems not so easy to trigger into it.

Also there are quite a number of references to this problem in various discussion groups. But no one really knows what is going on and what triggers the bug.

I found that it is needed to use multipart/form-data, have an <input type="file"> and have a long text in a textarea, which contains non-standard characters. Also having a javascript-submit helps it trigger.

other posts refering to this are for example:

http://www.houseoffusion.com/cf_lists/cache/4/23/23107.htm
http://mathforum.org/epigone/modperl/sweuphendbrong/1058388072.1311.58.camel@beast

i have the same problem with ie6 and a big form (multipart/form-data, select, BIG textarea with FCKEditor).
i used WPE (winsock packet editor) to capture the packets that IE generated and, yes, the problem is in IE.
sadly, this bug is very poorly documentated

I see this is an old discussion but I hope someone will discover my call for help.
There are lots of 'complains' on different web blogs concerning IE 6 or 7 sending form data twice. 
Most replies suggest that the user is hitting the submit button twice.
I don't think this always the case.
I am getting the problem almost permanently with both IE 6 and IE 7. but no problem with Firefox or Opera!
For info my form data is handled by php.
Only login name, password and submit are being sent.
I have made the receiving page record a log of it's activities and (only with IE) the page runs twice! 
The first time with all the $_POST variables empty. 
The second time they are populated with correct values.
These tests are made on a local Apache test setup.
The same thing happens on the live web site but the first time sometimes has corrupt data. 
The second time seems to be ok as on local test.
I am at a loss and can't find anything on the web which gets down to this problem.
Bob R.

Any ideas for a fix (apart of telling all users to go over to Firefox!).

I also face the same issue. check the below code.

 <body>
  <form method="post" action="fpost.php">
  <table>
  <tr>
	<td>Name</td>
	<td><input type="text" name="a[]" size="20"></td>
  </tr>
  <tr>
	<td>Name 1</td>
	<td><input type="text" name="a[]" size="20"></td>
  </tr>
  <tr>
	<td>Name 2</td>
	<td><input type="text" name="a[]" size="20"></td>
  </tr>
  <tr>
	<td>Name 3</td>
	<td><input type="text" name="a[]" size="20"></td>
  </tr>
  <tr>
	<td>Go</td>
	<td><input type="submit" value="Proceed"></td>
  </tr>
  </table>
  </form>

my print_r($_POST) returns as 

Array
(
    [a] => Array
        (
            [0] => a
            [1] => b
            [2] => c
            [3] => da[]=a
            [4] => b
            [5] => c
            [6] => d
        )

)

I get this issue on IE and Firefox.

Any Help