select option by XMLHttpRequest for language selection

Question

Please help me to work out this idea: I want to select language and refresh the page after selection and it should change the laguage for present page. My target: after selection from Dropdown list, I am getting the value by document.getElementById('language');and want to send this value to next page, named ajax_lang.php and set in that page the SESSION and after that want to get the Session to refresh the page with Session laguage.

I have copied the code which i tried.But failed. Please help me to work it out. thanks in advance. part 1.php code for session start: part 2: javascript part 3. html code part 4: ajax_lang.php

if(!isset($_SESSION)) 
     { 
         session_start();
                 
     }?>





<div style="margin-top:39px;background: #e9e9e9;margin-left:158px">
                        <select style="width: 40px;height: 40px;border-radius: 50%;width: 40px;
                                border: none;position: absolute;margin-top: 0px;" 
                                name="language" id="language" onchange="loadDoc(this.value)">
                              <option value=""><?php echo $_SESSION['lang'];?></option>
                              <option value="ru">RU</option>
                              <option value="en">EN</option>
                              
                        </select> 
                  </div>



<script>function loadDoc() {
      const xhttp = new XMLHttpRequest();
      xhttp.onreadystatechange = function() {
        if (this.readyState == 4 && this.status == 200) {
          document.getElementById("language").innerHTML =
          this.responseText;
        }
      };
      //xhttp.open("POST", "ajax_lang.php");
      xhttp.open("POST", "ajax_lang.php");
         var select = document.getElementById('language');
         var lang = select.options[select.selectedIndex].value;
         console.log(lang); // en

       xhttp.send({lang:lang});
    }
    //loadDoc();
    </script>



<?php 
if(!isset($_SESSION['lang'])){
session_start();
$_SESSION['lang']=$_POST['lang'];
}


?> ```

Answer 1

XMLHttpRequest.send does not take a plain object as a parameter, it takes either a string or a URLSearchParams object. See URLSearchParams example below.

xhttp.send(new URLSearchParams({lang:lang}));