web services

I haven't really used php in a while and I seem to be a little rusty. Let's say the following request is sent to my php page. How to I access the xml in my php script?

POST /myScript.php
Content-Type: text/xml
Content-Length: 557
User-Agent: myClient
Host: www.lalala.ca

<itemContainer>
... a bunch of xml here ...
</itemContainer>