Ajax request for PHP loop number - php

Question

I'm currently trying to get a PHP loop status and update a HTML5 progress bar.
The loop is triggered by a button click and set to 5000 with 1sec sleep() after every execution. I of course also made an Ajax request to which reuqests the current loop number every second and update the progress bar. However the request always waits until the loop is completed and shows me a number like "1234567891011..."
This is my JQuery code which is very simple because it's only for testing and learning purpose
function getStatus() {
$.ajax({
url : 'ajax.php',
dataType: "html",
type: "POST",
data: {request: 'request',},
success: function( data ) {
//Call function to update status on the loading bar
updateBar(data);
}
});
//Update loading bar
function updateBar(data) {
$('progress').attr('value', data);
}
}
function setGo() {
$.ajax({
url : 'ajax.php',
dataType: "html",
type: "POST",
//async: false,
data: {status: 'GO',},
success: function( data ) {}
});
}
$('#start').click(function(event) {
setGo();
setInterval(function() {
getStatus();
}, 1000);
});
This is my php Code
<?php
//Overwrite php execution limit
set_time_limit(120);
if($_POST['status'] = 'GO') {
$number = 5000;
$counter = 0;
for($i=0; $i != $number; $i++) {
$counter++;
sleep(1);
if(isset($_POST['request'])) {
echo $counter;
}
}
}
?>
I tried a lot of different ways and read a lot of posts but somehow nothing worked for me.
Hope someone got an idea.

Answer 1

Take a good look at your "echo $counter;" part in your PHP script, that's in a (5000 times) loop.

Answer 2

After the PHP code is interpreted and executed, the web server sends resulting output to its client, usually in form of a part of the generated web page – for example, PHP code can generate a web page's HTML code
From PHP's wiki page
This basically means that the whole php file will always be executed before returning the output. The loop will be executed 5000 times before returning the output.