PHP Outputting XML file

[chuy08]

I am trying to create an XML file using a PHP script. The XML File
looks something like this:

<?xml version="1.0" encoding="ISO-8859-1"?>
<ConsumerDirectXML>
<UserParams id="1" BrokerID="1"/>
<LoanParams>
<FirstLeinAmt>500000</FirstLeinAmt>
<ChooseProductTypeID>1</ChooseProductTypeID>
</LoanParams>
</ConsumerDirectXML>

The part that I don't understand is the following. I have a series of
checkboxes with each box having a different value. If a user were to
select 3 checkboxes I need to iterate through the array and write to
the ChooseProductTypeID field in the XML file as such,
<ChooseProductTypeID>1,5,7</ChooseProductTypeID>. I have been able to
print out the array variable $num using the following foreach loop:

foreach ($total as $num) {
print("$num,"); }

How would I get this string into the designated XML tag?

Currently I am able to write to this XML file using textboxes and the
following code for different XML tags in same file. How would I modify
what I am currently using for textboxes to use for the checkboxes while
utilitzing the foreach loop. Below is the method by which I am
writting to my XML file:

if ($node_name == "FirstLeinAmt") {
if ($value == $firstlein) {
// Do nothing
} else {
$fl_textnode = $child_obj->firstChild;
$new_firstlein = $doc->createTextNode($firstlein);
$child_obj->replaceChild($new_firstlein, $fl_textnode);
}
}
foreach ($total as $num) {
if ($node_name == "ChoosedProductTypeID") {
if ($value == $num) {
// Do nothing
} else {
$pt_textnode = $child_obj->firstChild;
$new_num = $doc->createTextNode("$num,");
$child_obj->replaceChild("$new_num", "$pt_textnode");
}}
....
Any help appreciated.