PHP - Flushing While Loop Data with Ajax

Question 1

Using PHP, I would like to make a while loop that reads a large file and sends the current line number when requested. Using Ajax, I'd like to get the current line count and print it out onto a page. Using html buttons, I'd like to be able to click and activate or terminate a javascript thread that runs only ONCE and calls the ajax method.

I have given it a shot but for some reason, nothing prints unless I comment out the echo str_repeat(' ',1024*64); function and when it's commented out, it shows the entire loop result:

1 row(s) processed.2 row(s) processed.3 row(s) processed.4 row(s) processed.5 row(s) processed.6 row(s) processed.7 row(s) processed.8 row(s) processed.9 row(s) processed.10 row(s) processed.

In a single line instead of showing them in separate lines like:

1 row(s) processed.
2 row(s) processed.
3 row(s) processed.
4 row(s) processed.
5 row(s) processed.
6 row(s) processed.
7 row(s) processed.
8 row(s) processed.
9 row(s) processed.
10 row(s) processed.

Also I'm not sure how to terminate the JavaScript thread. So 2 problems in total:

 1. It's returning the entire While loop object at once instead of each time it loops.
 2. I'm not sure how to terminate the JQuery thread.

Any ideas? Below is my code so far.

msgserv.php

<?php

//Initiate Line Count
$lineCount = 0;

// Set current filename
$file = "test.txt";

// Open the file for reading
$handle = fopen($file, "r");

//Change Execution Time to 8 Hours
ini_set('max_execution_time', 28800);

// Loop through the file until you reach the last line
while (!feof($handle)) {

    // Read a line
    $line = fgets($handle);

    // Increment the counter
    $lineCount++;

    // Javascript for updating the progress bar and information
    echo $lineCount . " row(s) processed.";

    // This is for the buffer achieve the minimum size in order to flush data
    //echo str_repeat(' ',1024*64);

    // Send output to browser immediately
    flush();

    // Sleep one second so we can see the delay
    //usleep(100);
}

// Release the file for access
fclose($handle);

?>

asd.html

<html>
    <head>
        <script src="http://code.jquery.com/jquery-latest.min.js" type="text/javascript" charset="utf-8"></script>

        <style type="text/css" media="screen">
            .msg{ background:#aaa;padding:.2em; border-bottom:1px #000 solid}
            .new{ background-color:#3B9957;}
            .error{ background-color:#992E36;}
        </style>

    </head>
    <body>

    <center>
        <fieldset>
            <legend>Count lines in a file</legend>
            <input type="button" value="Start Counting" id="startCounting" />
            <input type="button" value="Stop Counting!" onclick="clearInterval(not-Sure-How-To-Reference-Jquery-Thread);" />
        </fieldset>
    </center>

    <div id="messages">
        <div class="msg old"></div>
    </div>

    <script type="text/javascript" charset="utf-8">
        function addmsg(type, msg){
            /* Simple helper to add a div.
        type is the name of a CSS class (old/new/error).
        msg is the contents of the div */
            $("#messages").append(
            "<div class='msg "+ type +"'>"+ msg +"</div>"
        );
        }

        function waitForMsg(){
            /* This requests the url "msgsrv.php"
        When it complete (or errors)*/
            $.ajax({
                type: "GET",
                url: "msgsrv.php",
                async: true, /* If set to non-async, browser shows page as "Loading.."*/
                cache: false,
                timeout:2880000, /* Timeout in ms set to 8 hours */

                success: function(data){ /* called when request to barge.php completes */
                    addmsg("new", data); /* Add response to a .msg div (with the "new" class)*/
                    setTimeout(
                    'waitForMsg()', /* Request next message */
                    1000 /* ..after 1 seconds */
                );
                },
                error: function(XMLHttpRequest, textStatus, errorThrown){
                    addmsg("error", textStatus + " (" + errorThrown + ")");
                    setTimeout(
                    'waitForMsg()', /* Try again after.. */
                    "15000"); /* milliseconds (15seconds) */
                },
            });
        };

        $('#startCounting').click(function() {
            waitForMsg();
        });
    </script>

</body>
</html>

test.txt

Question 2

Using:

jQuery kill ajax request
ignore_user_abort()
ob_flush()

should do all you need in one php thread

EDIT

Take a look at nickb's answer, if you're looking for a way how to do this simply it would be following algorithm:

javascript opens process.php via ajax (which will do all the work AND print status reports), you have to look up whether jQuery ajax supports continuous loading
if user decides to stop refreshes you'll kill loading as show in provided link

In process.php:

ignore_user_abort(); // Script will finish in background
while(...){
  echo "Page: $in";
  ob_flush();
}

EDIT 2 requested example (bit of different and ugly, but simple). test_process.php:

// This script will write numbers from 1 to 100 into file (whatever happens)
// And sends continuously info to user
$fp = fopen( '/tmp/output.txt', 'w') or die('Failed to open');
set_time_limit( 120);
ignore_user_abort(true);

for( $i = 0; $i < 100; $i++){
    echo "<script type="text/javascript">parent.document.getElementById( 'foo').innerHTML += 'Line $i<br />';</script>";
    echo str_repeat( ' ', 2048);
    flush();
    ob_flush();
    sleep(1);
    fwrite( $fp, "$in");
}

fclose( $fp);

And main html page:

<iframe id="loadarea"></iframe><br />
<script>
function helper() {
    document.getElementById('loadarea').src = 'test_process.php';
}
function kill() {
    document.getElementById('loadarea').src = '';
}
</script>

<input type="button" onclick="helper()" value="Start">
<input type="button" onclick="kill()" value="Stop">
<div id="foo"></div>

After hitting start lines as:

Line 1
Line 2

Appeared in the div #foo. When I hit Stop, they stopped appearing but script finished in background and written all 100 numbers into file.

If you hit Start again script starts to execute from the begging (rewrite file) so would parallel request do.

For more info on http streaming see this link

Question 3

Build an array up as you iterate with the while loop.

$result = mysql_query("SELECT * FROM `Departments`");
$results = array();
while($row = mysql_fetch_assoc($result))
{
   $results[] = $row;
}

Alternatively, if you used PDO, you could do this automatically.

Question 4

Each time when mysqli_fetch_assoc($result) is accessed, the pointer moves to the next record. At last when no records are found, it returns null which breaks the while condition.

Question 5

to create a array, you need to first initialize it outside your loop (because of variable scoping)

$start = $day = strtotime("-1 day");
$end = strtotime('+6 day');
$dates = array(); //added
while($day < $end)
{
    $dates[] = date('d-M-Y', $day); // modified
    $day = strtotime("+1 day", $day) ;
}
echo "<pre>";
var_dump($dates);
echo "</pre>";

you can then use your dates using either foreach or while

foreach approach :

foreach($dates as $date){
     echo $date."<br>";
}

while approach :

$max =  count($dates);
$i = 0;
while($i < $max){
    echo $dates[$i]."<br>";
}

Question 6

I need to query by userId WHERE departmentId = XXXX and SUM each of their totalHours that exist, without neglecting the userId without any record in attendance.

To show the hours for all users in a given department, even users w/o rows in the attendance table, use a LEFT JOIN

Use (CAST(totalHours AS UNSIGNED) % 100)/60 + FLOOR(CAST(totalHours AS UNSIGNED)/100) to convert your varchar hours+minutes to a single number of hours.

$query = "SELECT u.id, 
SUM((CAST(totalHours AS UNSIGNED) % 100)/60 + FLOOR(CAST(totalHours AS UNSIGNED)/100)) grandTotal
FROM user u
LEFT JOIN attendance a
ON u.id = a.userId
WHERE u.departmentId = 2
GROUP BY u.id";

$result = mysqli_query($con,$query);

while($row = mysqli_fetch_array($result)) {
    print $row['id'] . ' ' . $row['grandTotal'];
}

PHP - Flushing While Loop Data with Ajax

Answers

php,ajax,loops,while-loop,flush