ajax upload file response with extra data - php

Question

I'm trying to add a file upload option to my page.
And I use Ajax for this purpose that sends the file to the server (where it is saved)
And should get back the file name
Everything works well except that when I print what comes back instead of just getting the array I send from the server I also get extra information.
Does anyone know where this supplement comes from? and how I can get rid of it?
here is my ajax:
$("#upload_file").change(function(input){
console.log(" in upload_file");
var file_data = $('#upload_file').prop('files')[0];
var form_data = new FormData();
form_data.append('file', file_data);
$.ajax({
type: 'POST',
url: '<?php echo base_url(); ?>organizer/save_event_file',
// dataType: 'text',
cache: false,
contentType: false,
processData: false,
data: form_data,
beforeSend: function(){
$('#progress_spinner').show();
$('body').addClass('disable_body');
},
success: function(response,status){
console.log(response);
},
complete: function(){
$('#progress_spinner').hide();
$('body').removeClass('disable_body');
}
}).fail(function (xhr, status, error) {
alert("error");
});//fail;
});
this is my server function:
enter code here
public function save_event_file(){ // to add check and prommision
$filePath = $_FILES['file']['tmp_name'];
$type=$_FILES['file']['type'];
//adding to the name with the current date in the end
$date = new DateTime();
$name = substr($_FILES['file']['name'],0,strpos($_FILES['file']['name'],'.')). '__' .$date>format('d.m.y').substr($_FILES['file']['name'],strpos($_FILES['file']['name'],'.'));
$data = array('file' => curl_file_create($filePath, $type, $name));
$response = $this->organizer_model->save_file($data); // save the file with the new name
$result = array('alertcode'=>1,'response'=>$response,'name'=>$name);
echo json_encode($result);
}
this is what I expect to be the response:
{"alertcode":1,"response":true,"name":"old db function__21.03.21.txt"}
this is the real response (The other part is the " {"alertcode":1}" in the beginning):
{"alertcode":1}{"alertcode":1,"response":true,"name":"old db function__21.03.21.txt"}
I have no problem cutting this information and then making a parse as follows:
var ans = JSON.parse(response.substring(response.indexOf('{"alertcode',10),response.length));
But I want to understand where this is coming from - in case this addition changes - and then it will cut the string badly.