<request> <action>getCategories</action> <params /> - php

Question

I got this code and I need to write additional code to make it work:
<ul>
<li>1</li>
<li>2</li>
</ul>
<hr>
<?php
$iTest = (int) $_GET['test'];
$sXML = '<?xml version="1.0" encoding="UTF-8"?>'."\n";
switch ($iTest) {
case 1:
$sXML .= '<request>
<action>getCategories</action>
<params />
</request>';
break;
case 2:
$sXML .= '<request>
<action>getProducts</action>
<params>
<catid>1</catid>
<page>1</page>
</params>
</request>';
break;
default:
exit();
break;
}
I actually understand what it should do but I need to write an input file that would do something according to the action send, how should I treat this :
<request>
<action>getProducts</action>
<params>
<catid>1</catid>
<page>1</page>
</params>
</request>
if it would be just a simple variable everything would be ok but now I dont get how to get around it
whats here is all clear to me, just send sXML to input and return result:
$oCurl = curl_init();
curl_setopt($oCurl, CURLOPT_URL, 'http://localhost/joboffer/input.php');
curl_setopt($oCurl, CURLOPT_POST, true);
curl_setopt($oCurl, CURLOPT_POSTFIELDS, $sXML);
curl_setopt($oCurl, CURLOPT_SSL_VERIFYPEER,false);
curl_setopt($oCurl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($oCurl, CURLOPT_FRESH_CONNECT, true);
curl_setopt($oCurl, CURLOPT_HTTPHEADER,
array(
'Content-type: text/xml; charset=UTF-8',
'Expect: '
)
);
$sRespond = curl_exec($oCurl);
$iRespondCode = curl_getinfo($oCurl, CURLINFO_HTTP_CODE);
curl_close($oCurl);
echo '<pre>RESPOND ', $iRespondCode, "\n\n", htmlentities($sRespond);