sorting form fields

[Anon]

I am having problems when sorting form fields. I need keys from $HTTP_POST_VARS which are in alphabetical order.
I have tried following kind of code:

$in = $HTTP_POST_VARS;
if ($in['sort_order'] == 'alphabetic') {
$sorted_fields = ksort(array_keys($in));
}

But it gives following kind of error: Invalid argument supplies for foreach().
Like you may have noticed I use foreach to loop though the keys in $sorted_fields because it is the best choice for my purposes. What should I do so that it would work correctly when using foreach()?

[Anon]

Can you post the part of code including the "foreach()" please ?

Thanx

JBL

[Anon]

Here is the foreach() part of the code:

foreach ($sorted_fields as $sorted_field) {
if (!in_array($sorted_field, $params)) {
if ($in[$sorted_field]) {
if (is_array($in[$sorted_field])) {
$array_values = implode(', ', $in[$sorted_field]);
$message .= "$sorted_field: $array_values\n";
}
else {
$message .= "$sorted_field: $in[$sorted_field]\n";
}
}
}
}

There might be some spelling mistakes in the code because I writed it, not copiend.