function Estimation(){
  var xhr=getXhr();

  xhr.onreadystatechange=function(){
    if(xhr.readyState==4 && xhr.status==200){
      var reponse=xhr.responseText;

      document.getElementById('id_estimation').innerHTML=reponse;
    }
  }

  xhr.open("POST","estimation.php",true);
  xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
  var debut_jour=document.getElementById('id_date_debut[0]').value;
  var debut_mois=document.getElementById('id_date_debut[1]').value;
  var debut_annee=document.getElementById('id_date_debut[2]').value;
  var fin_jour=document.getElementById('id_date_fin[0]').value;
  var fin_mois=document.getElementById('id_date_fin[1]').value;
  var fin_annee=document.getElementById('id_date_fin[2]').value;
  xhr.send("debut_jour="+debut_jour+"&debut_mois="+debut_mois+"&debut_annee="+debut_annee+"&fin_jour="+fin_jour+"&fin_mois="+fin_mois+"&fin_annee="+fin_annee);
}