Ajax never initiating success: when using xhrFields - php

Question

I am having trouble getting the success call to fire in my ajax request. I know the communication is working fine, but the last call in my PHP script, which is a return json_encode($array); will fire as if it is a part of the onprogress object. I would like to "break" the onprogress call and run the success function on the last data sent via return json_encode when the PHP script has terminated...
Here is my AJAX call:
$( document ).ready(function(e) {
var jsonResponse = '', lastResponseLen = false;
$("#btn_search").click(function(e){
var firstname = document.getElementById('firstname').value;
var lastname = document.getElementById('lastname').value;
$.ajax({
type: "POST",
url: 'search.php',
data: $('#search_fields').serialize(),
dataType: "json",
xhrFields: {
onprogress: function(e) {
var thisResponse, response = e.currentTarget.response;
if(lastResponseLen === false) {
thisResponse = response;
lastResponseLen = response.length;
} else {
thisResponse = response.substring(lastResponseLen);
lastResponseLen = response.length;
}
jsonResponse = JSON.parse(thisResponse);
document.getElementById('progress').innerHTML = 'Progress: '+jsonResponse.msg;
}
},
success: function(data) {
console.log('done!');
document.getElementById('progress').innerHTML = 'Complete!';
document.getElementById('results').innerHTML = data;
}
});
e.preventDefault();
});
});
And here is the basic PHP server script:
<?php
function progress_msg($progress, $message){
echo json_encode(array('progress' => $progress, 'msg' => $message));
flush();
ob_flush();
}
$array = array('msg' => 'hello world');
$count = 0;
while($count < 100){
progress_message($count, "working....");
$count += 10;
sleep(2);
}
return json_encode($array);
?>

Answer 1

I made your code work, there were 2 errors. First, in your while loop, your function name is incorrect, try this:
progress_msg($count, "working... ." . $count . "%");
Secondly, the very last line outputs nothing, so technically you don't get a "successful" json return. Change the last line of your server script from:
return json_encode($array);
to:
echo json_encode($array);
UPDATE: Full working code with hacky solution:
Ajax:
$( document ).ready(function(e) {
var jsonResponse = '', lastResponseLen = false;
$("#btn_search").click(function(e){
var firstname = document.getElementById('firstname').value;
var lastname = document.getElementById('lastname').value;
$.ajax({
type: "POST",
url: 'search.php',
data: $('#search_fields').serialize(),
xhrFields: {
onprogress: function(e) {
var thisResponse, response = e.currentTarget.response;
if(lastResponseLen === false) {
thisResponse = response;
lastResponseLen = response.length;
} else {
thisResponse = response.substring(lastResponseLen);
lastResponseLen = response.length;
}
jsonResponse = JSON.parse(thisResponse);
document.getElementById('progress').innerHTML = 'Progress: '+jsonResponse.msg;
}
},
success: function(data) {
console.log('done!');
dataObjects = data.split("{");
finalResult = "{" + dataObjects[dataObjects.length - 1];
jsonResponse = JSON.parse(finalResult);
document.getElementById('progress').innerHTML = 'Complete!';
document.getElementById('results').innerHTML = jsonResponse.msg;
}
});
e.preventDefault();
});
Search.php:
<?php
function progress_msg($progress, $message){
echo json_encode(array('progress' => $progress, 'msg' => $message));
flush();
ob_flush();
}
$array = array('msg' => 'hello world');
$count = 0;
while($count <= 100){
progress_msg($count, "working... " . $count . "%");
$count += 10;
sleep(1);
}
ob_flush();
flush();
ob_end_clean();
echo json_encode($array);
?>
The problem with the "success" method of the ajax call was that it couldn't interpret the returning data as JSON, since the full return was:
{"progress":0,"msg":"working... 0%"}{"progress":10,"msg":"working... 10%"}{"progress":20,"msg":"working... 20%"}{"progress":30,"msg":"working... 30%"}{"progress":40,"msg":"working... 40%"}{"progress":50,"msg":"working... 50%"}{"progress":60,"msg":"working... 60%"}{"progress":70,"msg":"working... 70%"}{"progress":80,"msg":"working... 80%"}{"progress":90,"msg":"working... 90%"}{"progress":100,"msg":"working... 100%"}{"msg":"hello world"}
Which is not a valid JSON object, but multipje JSON objects one after another.
I tried removing all previous output with ob_end_clean(); , but for some reason I can't figure out, it didn't work on my setup. So instead, the hacky solution I came up with was to not treat the return as JSON (by removing the dataType parameter from the AJAX call), and simply split out the final Json element with string operations...
There has got to be a simpler solution to this, but without the use of a third party jQuery library for XHR and Ajax, I couldn't find any.