function testXMLHTTP(){
    var docXML = loadXMLDoc("dummy.xml", false);
    postXMLDoc(docXML, "./echo.php", true);//"ciao"
}

///////////////// xmlhttp section ///////////////////
function initReq(){
    if (window.req){
        req.abort();
    }
    //delete req;
    // branch for native XMLHttpRequest object
    if (window.XMLHttpRequest) {
      req = new XMLHttpRequest();

  // branch for IE/Windows ActiveX version
  } else if (window.ActiveXObject) {
          //"Msxml2.XMLHTTP.4.0"
          //"Microsoft.XMLHTTP"
      req = new ActiveXObject("Msxml2.XMLHTTP.4.0");
  }
 }


function postXMLDoc(doc, url, async){
    //initReq();
    //async = true;
    if (async){
      req.onreadystatechange = postReqChange;
  }
  req.open("POST", url, async);
  req.setRequestHeader('content-type', 'text/xml');
  req.send(doc);
  if (!async){
      alert("mandato: "+req.responseText);
  }
  else{
      alert("aspetta");
  }
}

function postReqChange() {
  // only if req shows "loaded"
  if (req.readyState == 4) {
    // only if "OK"
    if (req.status == 200) {
      alert(req.responseText);
    } else {
            alert("There was a problem retrieving the XML data:\n" +req.statusText);
    }
  }
}


///////////php script//////////////// (echo.php)

<?php
            $sXML = $GLOBALS['HTTP_RAW_POST_DATA'];

      echo "$sXML";

      // Open a text file and erase the contents if any
      $fp = fopen("posted.xml", "w");

      // Write the data to the file
      fwrite($fp, $sXML);

      // Close the file
      fclose($fp);


      //$headers = getallheaders();
      /*foreach ($headers as $name => $content) {
      echo "$name = $content<br>n";
      }*/
      //echo "{$headers["my-header"]}";
    ?>


//////////////////////xml document////////////////////// (dummy.xml)

<progetto id="0"><schema id="schF0" tipo="schemaFunzionale"><schemaFunzionale/><oggetto id="imm0" tipo="immagine" x="50" y="50"><immagine nomeFile="cacca.jpg"/><etichettaAssociata id="etich0"/></oggetto><oggetto id="etich0" tipo="etichetta" x="100" y="100"><etichetta idOggettoEtichettato="imm0">commento cacca</etichetta></oggetto></schema></progetto>