showing download progress while downloading a file using PHP and jquery

Question

I am developing a download manager using PHP and jquery.

Requested a script that will download a file and also show the download progress.

I tried the following, but it not works

Jquery

function downloadFile(){
    var fileNameDownloading ="somefile.mp3"
    var oReq = new XMLHttpRequest();    
    oReq.addEventListener("progress", updateProgress, false);
    var params = "filename="+fileNameDownloading;   
    oReq.open("GET", "scripts/download.php?"+params, true);
    oReq.responseType = "blob";//blob arraybuffer

    function updateProgress (e) {
        console.log(e.loaded/e.total);
    }
    oReq.send();    
}

PHP

<?php
$file = $_GET['filename'];
$fileSize = get_size($file);
$packetSize = 262144;//2000
if($packetSize > $fileSize){
    $packetSize = $fileSize;
}
download($file,$packetSize);


function download($file,$chunks){
    set_time_limit(0);
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-disposition: attachment; filename='.basename($file));
    header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
    header('Expires: 0');
    header('Pragma: public');
    $size = get_size($file);
    header('Content-Length: '.$size);

    $i = 0;
    while($i<=$size){
        //Output the chunk
        get_chunk($file,(($i==0)?$i:$i+1),((($i+$chunks)>$size)?$size:$i+$chunks));
        $i = ($i+$chunks);
    }

}

//Callback function for CURLOPT_WRITEFUNCTION, This is what prints the chunk
function chunk($ch, $str) {
    
    print($str);
    return strlen($str);
}

//Function to get a range of bytes from the remote file
function get_chunk($file,$start,$end){
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $file);
    curl_setopt($ch, CURLOPT_RANGE, $start.'-'.$end);
    curl_setopt($ch, CURLOPT_BINARYTRANSFER, 1);
    curl_setopt($ch, CURLOPT_WRITEFUNCTION, 'chunk');
    $result = curl_exec($ch);
    curl_close($ch);
}

//Get total size of file
function get_size($url){
    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $url);
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_HEADER, true);
    curl_setopt($ch, CURLOPT_NOBODY, true);
    curl_exec($ch);
    $size = curl_getinfo($ch, CURLINFO_CONTENT_LENGTH_DOWNLOAD);
    return intval($size);
}
?>

Looking for a suggestion, how we can download a file and also show download progress using PHP and javascript. Thanks

Solution

Two possible methods include using either polling or the uploadProgress ajaxSubmit option.

Using ajax / javascript polling, you would have a setTimeout every second that calls a server file and sees how much data has been written to the server. This article should help provide a good example and description of polling. The callback would set the progress based on the file size.

The second method is using the uploadProgress ajaxSubmit option. This article will give a good tutorial for how to set this up.

The following is a code example:

jQuery:

$(document).ready(function() {  
var options = { 
        target:   '#output', 
        beforeSubmit:  beforeSubmit,
        uploadProgress: OnProgress, //upload progress callback 
        success:       afterSuccess,
        resetForm: true  
    }; 
    
 $('#MyUploadForm').submit(function() { 
        $(this).ajaxSubmit(options);            
        return false; 
    });
});

function OnProgress(event, position, total, percentComplete)
{
    //Progress bar
    progressbar.width(percentComplete + '%') //update progressbar percent complete
    statustxt.html(percentComplete + '%'); //update status text
    if(percentComplete>50)
        {
            statustxt.css('color','#fff'); //change status text to white after 50%
        }
}

HTML:

<div id="upload-wrapper">
<div align="center">
<h3>Ajax Image Uploader with Progressbar</h3>
<span class="">Image Type allowed: Jpeg, Jpg, Png and Gif. | Maximum Size 1 MB</span>
<form action="processupload.php" onSubmit="return false" method="post" enctype="multipart/form-data" id="MyUploadForm">
<input name="ImageFile" id="imageInput" type="file" />
<input type="submit"  id="submit-btn" value="Upload" />
<img src="images/ajax-loader.gif" id="loading-img" style="display:none;" alt="Please Wait"/>
</form>
<div id="progressbox" style="display:none;"><div id="progressbar"></div ><div id="statustxt">0%</div></div>
<div id="output"></div>
</div>
</div>

CSS

#progressbox {
border: 1px solid #0099CC;
padding: 1px; 
position:relative;
width:400px;
border-radius: 3px;
margin: 10px;
display:none;
text-align:left;
}
#progressbar {
height:20px;
border-radius: 3px;
background-color: #003333;
width:1%;
}
#statustxt {
top:3px;
left:50%;
position:absolute;
display:inline-block;
color: #000000;
}