title: HTTP Post command with XML request (PHP)
body: <p>I'm working on a system which needs to integrate with an external (commercial) system.  On my site, I have some information, and then that needs to be checked against the external system's records.  This is done by posting an XML request.</p>
  
  <p>I can't make sense of their documentation.  They've given me some example xml, but I just don't know what to do with it.  Can anyone help?!  I can't find much online that tells me what to do.</p>
  
  <p>I'm using PHP, and the request has to be POSTed via HTTPS.  The xml I've been given is (roughly - can't give the full details due to security):</p>
  
  <pre><code>&lt;?xml version="1.0" standalone="no" ?&gt;
  &lt;request&gt;
    &lt;request_header interface_version_no="0.2" dtd_version_no="0.2"&gt;
      &lt;client_reference&gt;Test Client&lt;/client_reference&gt;
    &lt;/request_header&gt;
    &lt;service_request id="1"&gt;
      &lt;session_service&gt;
        &lt;logon_request domain_id="******" user_id="******" password="******"/&gt;
      &lt;/session_service&gt;
    &lt;/service_request&gt;
  &lt;/request&gt;
  </code></pre>
  
  <p>The code above should log me in to their system.  So, my questions are:</p>
  
  <ol>
  <li>What do I actually do with this?  How do I make it into a POST request?</li>
  <li>What do I do with the response (which is also xml)?  I have parsed xml before (using XSLT), but that was to display it... is there a standard way of doing it in PHP?</li>
  </ol>
  
  <p>Thanks!  Any help is appreciated.  I can't find much online (well, I can find loads, but none of it seems to be specific to what I'm looking for, so I'm getting confused), so even links to the appropriate help pages would be great.</p>