<style>
.dataContainer{
  background-color: red;
  width: 185px;
  position: relative;
}

.dataContainerDesign #a,#b,#send{
  display: block;
  margin: auto;
}
</style>

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<script>
$(document).ready(function(){
  $('.dataContainer #send').click(function(){
    //Per data container
    var $dataContainer = $(this).next('.dataContainer');
    //

    //Var data structure
    var a= $('.dataContainer #a').val();
    var b= $('.dataContainer #b').val();
    //

    //Data to be sent
    var Data= {
      a: a,
      b: b
    }
    //

    //Result after sending
    var Result= function(success){
   $dataContainer.html(success);
    }
    //

    //Request
    $.ajax({
      type: 'POST',
      data: Data,
      url: 'x.php',
      success: Result
    });
    //

  });
});
</script>

<div class='dataContainer dataContainerDesign'>
  <input id='a' type='text'>
  <input id='b' type='text'>
  <button id='send'>Send</button>
</div><!--</dataContainer>-->

<div class='dataContainer dataContainerDesign'>
  <input id='a' type='text'>
  <input id='b' type='text'>
  <button id='send'>Send</button>
</div><!--</dataContainer>-->

<div class='dataContainer dataContainerDesign'>
  <input id='a' type='text'>
  <input id='b' type='text'>
  <button id='send'>Send</button>
</div><!--</dataContainer>-->

<div class='dataContainer dataContainerDesign'>
  <input id='a' type='text'>
  <input id='b' type='text'>
  <button id='send'>Send</button>
</div><!--</dataContainer>-->

<p style='display: inline-block;'>
<?php
$a= $_POST['a'];
$b= $_POST['b'];
echo 'Sent Values: ';
echo $a.','.$b;
?>
</p>

<?php

/*<Insert values in Data Base>*/

$db_servername = 'localhost';
$db_username = 'jd';
$db_password = '1234';
$db_name = 'xxx';

$db_connect = new mysqli($db_servername, $db_username, $db_password, $db_name);

$db_query = "INSERT INTO sometable (a,b) VALUES ('$a','$b')";

$db_result= $db_connect->query($db_query);

/*</Insert values in Data Base>*/

?>