jquery - Ajax request cause following : Failed to load resource: the server responded with a status of 500 (Internal Server Error) -

i know there lot of related article on , had tried of suggestions other sharing. here partial listing of code

$(document).ready(function() {     $("#cron").click(function(event) {          $('.update-body').html('<br />performing updates...<br />')         event.preventdefault();         event.stoppropagation();         var request = $.ajax({            url: 'http://xx.xx.xx.xx/update/longprocessing',            type: "get",            contenttype: "application/json",            beforesend: function (xhr) {            var token = $('meta[name="csrf_token"]').attr('content');             if (token) {              return xhr.setrequestheader('x-csrf-token', token);            }        },        datatype: "json"     });      request.done(function(status) {        var msg = "";        if(status.msg == '1')        {            msg = '<div class="alert alert-success">successfully updated.</div>';        }        else if(status.msg == '2')        {            msg = '<div class="alert alert-info">no updates</div>';        }        $('.update-body').html(msg);    });     request.fail(function(jqxhr, textstatus) {      var acc = []      $.each(jqxhr, function(index, value) {        acc.push(index + ': ' + value);    });    $('.update-body').html('<div class="alert alert-danger">' json.stringify(acc) + '</div>');    });  }); }); 

processing.php expected takes average of 40 minute complete. here problem, code runs , success message returned when run xampp on windows 10 platform.

when move code linux under xampp, processing.php shows no error , runs fine (so nothing wrong php code) when monitor network performance, when waiting (ttfb) time first byte hit 15 minutes, following error message : failed load resource: server responded status of 500 (internal server error) generated somewhere in jquery ajax code. using jquery1.12.3.

any appreciated.

i realize sometimes, php function called first time , after 6 minute, called second time followed 503 service not available. not happen in xampp under windows happens in linux. using laravel 5.2 framework follows:

route::get('/update/longprocessing', ['as' => 'updateprocess', 'uses' => 'project\processjobs@updateprocess']); 

in processjobs.php, code follows:

public function updateprocess () {           log::debug("update process started");            $counter =0;           //get path linux folder            ...           //loop through folder 35000 csvfiles            foreach (xxx xxx) {             //for each file, read content, process , write single common csv files.               $counter++;               log::debug("counter value : " . $counter);            }           return response()->json(['msg'=>'1']); } 

log file shows following:

update process started counter value : 1 counter value : 2 counter value : 3 ... ... counter value : 10000 update process started    <--- second time called counter value : 10001     <--- counter still continue previous. counter value : 10002     <--- log file stop here , server return 503 service unavailable error.