Php script is automatically being invoked multipletimes

I think that I know what the reason, PHP writes session variables to file, but it do it only on end of script execution, so you can`t see the changes of session in another script before end of long one.

You can fix it by adding session_write_close(); session_start(); after each change of session data.

session_write_close will write changes to HD, so another script can read it. session_start will load session from HD, but make sure that your another script make no changes for a session, these changes will be overwritten by your long script.

And one more thing if you are using separate domains: Before actual AJAX call happen your browser sends OPTIONS request to the same URL for checking CORS headers. So on start of your script check the HTTP METHOD and if it HEAD or OPTIONS make die();

Instead of using sessions, try using a temp file to keep count with a dynamic ID

Javascript

var time = Date.now();
$.get('/firstURL?time='+time);
setInterval(function(){
    $.get('/secondURL?time='+time, function(response){
        console.log(response);
    }
}, 1000);

PHP 1st URL

<?php

$id = $_GET['time'];
$count = 0;

while(...) {
    // Do your stuff

    $count++;
    file_put_contents("/tmp/{$id}", $count);
}

?>

PHP 2nd URL

<?php

$id = $_GET['time'];
$count = 0;

try {
    $count = file_get_contents("/tmp/{$id}");
} catch(Exception $e) {}

echo $count;

?>

As other have said PHP does not write the session until execution has finished. you better off creating a php function that you call that writes a file with the progress and then your second ajax call just reads the file.

function updateCreateProgress($jobStartTime, $progress){
    file_put_contents('/tmp/'.$jobStartTime.'.txt', $progress);
}

function completeProgress($jobStartTime){
    unlink('/tmp/'.$jobStartTime.'.txt')
}

now your second script can check for '/tmp/'.$jobStartTime.'.txt' if it's there read it using file_get_contents if its not there report back it has finished.

Try adjusting to something like this:

$i=0;
ini_set('session.use_only_cookies', false);
ini_set('session.use_cookies', false);
ini_set('session.use_trans_sid', false);
ini_set('session.cache_limiter', null);
session_start();
 $_SESSION['time']=date('m-d-Y H:i:s');
 while(...)
 {

     $_SESSION['tracksatus']="loop number : ".$i." time is :"$_SESSION['time'];
     session_write_close();
     session_start();
     $i++;

     ......
     ......
 }

You started talking about $_SESSION before calling session_start();

If you call ajax with GET method - you must set "cache:false" option.

Yes, you must protect your php script from other requests. With unique key (GET parameter) or session.

php lock session data for single call and release it only when this call end. Using session_write_close() when script still working - bad practice. Maybe you want save into session something more after loop but before using this data from other requests.

Flexible and clear solution:

1) script1.php - invoke from ajax for start long job.

2) script2.php (long job here) - run directly from script1.php as background without wait, or add new cron job (insert into table) and run script2.php from cron (check jobs every second or other time).

3) script3.php - check job status (ajax).

For "communication" between script2.php and script3.php can be use database or special file with flock(), clearstatcache() and flush().