如何在未完成时从ajax触发的PHP调用获取更新？

Is there a way to get updates from a PHP process while it's not finished and it has been called by ajax? By updates i mean flushed output from the PHP script.

var proc;
$('#start').click(function () {
    proc = $.ajax({
        type: 'POST',
        url: 'execute.php',
        // getData function that will get me updated data
        getData: function (update){
            alert(update);
        }
    });
});

UPDATE: Lets say we want to get that echo before this ends.

execute.php

<?php
$progress = 0;
while(1){
    $progress++;
    echo $progress;
    flush();
    sleep(5);
    if($progress == 100){
        break;
    }
}
?>

FINAL:

myScript.js

var strongcalcs;
var source;
$('#start').click(function () {
    strongcalcs = $.ajax({
        type: 'POST',
        url: 'execute.php',
        beforeSend: function () {
            rpm_percent();
        },
        success: function(result){
            source.close();
        },
        complete: function () {
            source.close();
        },
        error: function () {
            source.close();
        }
    });
});

function rpm_percent() {
    source = new EventSource("execute.php");
    if(typeof(EventSource) !== "undefined") {
        source.onmessage = function(event) {
            console.log(event.data);
        };
    } else {
        alert("nono");
    }
}

execute.php

<?php
$coco = 0;
function sendMsg($msg, &$coco) {
    echo "id: " . $coco . "
";
    echo "data: " . $msg;
    echo "
";
    echo "
";
    ob_flush();
    flush();
    $coco++;
}

header("Content-Type: text/event-stream");
header("Cache-Control: no-cache");
$progress = 0;
while(1){
    sendMsg($progress++, $coco);
    ob_flush();
    flush();
    sleep(5);
    if($progress == 100){
        break;
    }
}
?>

I've in the past used Server Sent Events for this (https://www.w3schools.com/html/html5_serversentevents.asp). Internet Explorer is not supported out of the box, but there are polyfills that can solve the issue.

I think Websockets do something similar but don't have experience with those myself.

you can use Ajax callback when success load file from server..

$('#start').click(function () {
    proc = $.ajax({
        type: 'POST',
        url: 'execute.php',
        success: function (respon){
            //do what u want to do here.
            if(respon.status == 0){
              alert("failed");
            }
            else{
              alert("ok");
            }
        },
        error: function(xhr, error){
           //for error handling
        }
    });
});

and in your php you can echo what u want to show

<?php
  $var["status"] = 0;
  //if(your condition){ $var["status"] = 1;}
  return json_encode($var);
?>

for more information you can see on here and here