Transfer blob Image between mysql database and HTML using AJAX and Jquery - php

Question

My problem is not being able to encode the image properly after retrieving it from the database otherwise all my work is fine. After I fetch the image I managed to display it at the same php file using "header('content-type: image/jpeg')".
<?php
header('content-type: image/jpeg');
if($_SERVER['REQUEST_METHOD']=='GET'){
$id = $_GET['id'];
$sql = "select image from images order by id desc limit 1";
require_once('connection.php');
$r = mysqli_query($con,$sql);
$result = mysqli_fetch_array($r);
echo base64_decode($result['image']);
mysqli_close($con);
}else{
echo "Error";
}
?>
The previous piece of code is for displaying directly but it was for testing only, I need to use it as a JSON source so I modified it in this way:
header('Content-type: application/json');
.
.
.
$r['a'] = base64_encode( $result['image']);
echo json_encode($r);
For the Jquery and Ajax part also worked fine and I tested it by making another json file and put an image encoded professionally by this website https://www.base64-image.de/.
And here is Jquery code:
$(document).ready(function(){
(function()
{
d='';
var poll=function()
{
$.ajax({
url: "getjson.php",
type :"get",
dataType: "JSON",
success: function(json)
{
d +='data:image/jpeg;base64,';
d +=json.a;
$("#myimg2").attr("src",d);
}
})
};
poll();
setInterval(function(){
poll();
}, 2000);
})();
});
What I need now is to encode the image just like what this website does https://www.base64-image.de/ because this line base64_encode( $result['image']) seems to be not enough, I have tried many solutions available online but no one worked for me!