This is my ajax.php
I try to pass source1 to other php I got error when I use
$data = json_decode($_POST['source1']);
It says Undefined index. What should I do?
<?php 
session_start();
$data = json_decode($_POST['source1']);
 ?> 
<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
  <title></title>
</head>
<!-- <form action="sendinto.php" method="post"><center>
<button id="btnSelectedRows" type="button">test send</button>
</center>
</form> -->
<center>
      <button id="btnSelectedRows" >test</button>
    <!-- input type="submit" name="upload" value="Compare"> -->
  </center>
<body>
</body>
</html>
<script type="text/javascript">
this is my ajax code
$('#btnSelectedRows').on('click', function() {
 $.post({
  type: "POST",
  url: 'sendinto.php',
  datatype : 'text',
  data: {source1 : "heyo"} ,
   // or GET
}).done(function(data) {
    //Redirect to another page if you want...
    window.location.href = "sendinto.php";
   });
  });
this is my sendinto.php
<?php 
  session_start();
  $coba = $_SESSION['source1'];
  echo $coba;
?>
 
     
     
    