发送两个值到ajax查询

I need to send two parameter to my javascript and get the parameters in the php file how I can do it ?

My html :

<form method="post" action="testButtonSup.php">
        <p>
           Veuillez choisir le service<br />
           <input type="radio" name="service" value="ncli" id="ncli" checked ="checked" /> <label for="ncli">Ncli</label>
           <input type="radio" name="service" value="fcli" id="fcli" /> <label for="fcli">Fcli</label>
        </p>
        <p>
            <label for="client">Veuillez choisir le fournisseur :</label><br />
               <select name="client" id="client" onchange="showUser(this.value, service)">
                    <?php 
                        // echo '<option value=""/></option>';
                        while ($donnees = $reponse->fetch())
                        {               
                            echo '<option value='.$donnees['refCustomer'].'>'.$donnees['legalCompanyName'].' </option>';
                            $idClient = $donnees['refCustomer'];                                
                            //$value = $donnees['refCustomer'];                     
                        }


                        $reponse->closeCursor();
                    ?>              
               </select>
            </p>
        <p>.....

I want to send to the function showUser(this.value, service) two parameters : the id of the select and the value of the radio button "service" whic is up

My function :

function showUser(str, service) {
        if (str == "") {
            document.getElementById("txtHint").innerHTML = "";
            return;
        } else { 
            if (window.XMLHttpRequest) {
                // code for IE7+, Firefox, Chrome, Opera, Safari
                xmlhttp = new XMLHttpRequest();
            } else {
                // code for IE6, IE5
                xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
            }
            xmlhttp.onreadystatechange = function() {
                if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
                    document.getElementById("txtHint").innerHTML = xmlhttp.responseText;
                }
            }
            xmlhttp.open("GET","getTableBuffer.php?q="+str+"&service="service,true);
            xmlhttp.send();
        }
    }

I tried like this but it doesn't work.

in my php file it didn't recognize the parameter.

It works with only the id of the select.

If you can use jQuery (which I recommend to handle ajax request) you can do it this way:

function showUser(str, service) {
  if (str == "") {
    document.getElementById("txtHint").innerHTML = "";
    return;
  } else { 
    $.ajax({
      url: 'getTableBuffer.php',
      type: 'GET',
      data: {q:str, service:service}
    }).done(function(response){
      // Code to execute once the call has been executed
      $('#txtHint').html(response.responseText);
    });
  }
}

Without jQuery, a smallish function to get the value of a radio button from the collection to use in the ajax parameters.

    function radiovalue(name){
        var col=document.querySelectorAll('input[type="radio"]');
        for( var n in col )if( n && col[n] && col[n].nodeType==1 && col[n].type=='radio' ){
            if( col[n].hasAttribute('name') && col[n].getAttribute('name')==name ){
                if( col[n].checked ) return col[n].value;
            }
        }
        return false;
    }

   eg:
   ---
   xmlhttp.open("GET","getTableBuffer.php?q="+str+"&service="+radiovalue('service'),true);