PHP SOAP Request is missing XML Nodes

i need some help with a SOAP request. I need to send a XML through a SOAP WebService. It's working kind of ok. BUT!!! It's a shopping cart, when it only has one produt, it works like a charm, but when there's more than one. The SOAP request ignores the all the other and only send one. Here is the XML i'm trying to send.

<?xml version="1.0" encoding="utf-8"?>
<WSFAT1PP>
    <PREPV>
        <CNPJ>1</CNPJ>
        <CODORC>0000000025</CODORC>
        <ITEM>
            <FORMITEM>
                <CODPROIT>235060</CODPROIT>
                <QUANT>1</QUANT>
            </FORMITEM>
            <FORMITEM>
                <CODPROIT>339746</CODPROIT>
                <QUANT>1</QUANT>
            </FORMITEM>
        </ITEM>
        <OBS></OBS>
    </PREPV>
</WSFAT1PP>

And here is what's actually being sent:

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://ift.tt/sVJIaE" xmlns:ns1="http://xxx.xxx.xxx.xxx:xxxx/">
    <SOAP-ENV:Body>
        <ns1:WSFAT1PP>
            <ns1:PREPV>
                <ns1:CNPJ>1</ns1:CNPJ>
                <ns1:CODORC>0000000025</ns1:CODORC>
                <ns1:ITEM>
                    <ns1:FORMITEM>
                        <ns1:CODPROIT>235060</ns1:CODPROIT>
                        <ns1:QUANT>1</ns1:QUANT>
                    </ns1:FORMITEM>
                </ns1:ITEM>
                <ns1:OBS></ns1:OBS>
            </ns1:PREPV>
        </ns1:WSFAT1PP>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

The second produt is gone, and I have no idea why.

The code is the following

$xml = new SimpleXmlElement($xml);
$client = new SoapClient($url, array('trace' => 1));
try{
   $result = $client->WSFAT1PP($xml->asXML());
...