I was wondering how to accomplish an effect I've seen on several websites, where I click a download now link, it takes me to another page, and the download starts automatically. What is the best way to accomplish this?
Redirect to a page which emits the following headers:
header("Content-Disposition: attachment; filename=$filename");
header("Content-Length: $length");
See this post about the restrictions on $filename.
edit in response to andr's answer, the php equivalent of redirect-after-x-seconds would be:
header("Refresh: 2; url=start_download.php");
(although you should officially specify a complete URL, I think) where start_download.php would contain the two lines above.
First you show the page with some content (please wait, blah blah) and then redirect to the file itself or to the script which outputs the file.
The redirect is done either via meta tag or javascript:
html: <meta http-equiv="refresh" content="5;url=http://example.com/foo.zip" /> where «5» is in seconds
js on page load: setTimeout("location.href=http://example.com/foo.zip", 5000) where «5000» is in milliseconds.
If you choose to output the file via php script, follow mvds's answer.
Related
On a page where I offer music sample downloads, I have several <a> tags whose href points to a PHP file. Various data included as GET vars allow the proper file to be downloaded. Normally the PHP will respond with typical download headers followed by a readfile(). (the code for that is below, FYI). This results in a clean download (or download / play dialog box on some browsers). By "clean", I mean the download is completed with no disturbance in the visitors page.
However, in the unlikely event that the requested file is unavailable, I don't know what to do. I know it should not happen, but if it does I would like the download link to simply do NOTHING. Unfortunately since it is an <a> tag referencing a PHP file, doing nothing results in the browser clearing the page, with the URL of the PHP file in the address bar. Not a good visitor experience! So I'd like way to avoid disturbing the page and doing NOTHING if there is is an errant request. I'll use javascript to alert the visitor about what went wrong, but I can't have the errant file request clear the page!
I thought I'd had a solution by issuing a header('Location: #'); when the script detected an impossible file download. But after a few seconds the browser cleared the page and put up a message indicating the page "redirected you too many times." (indeed, my script log fills up with over 100 entries, even though i only clicked the tag once.)
So far the only solution I have that works (works in the sense of NOT disturbing the visitors page if an "unavailable" file is requested) is to point my download headers at a "dummy" file. An actual "silence.mp3" or "nosong.mp3" file. But is there a way to call a header() that does nothing to the calling page? Simply calling exit or exit() won't work (the visitor page is redirected a blank.)
Not that it matters, but this is the code I normally call in response to the d/l request...
function downloadFile($path) {
$path_parts = pathinfo($path);
$ext = strtolower($path_parts["extension"]); // don't need this.
$fsize =fileExists($path);
if ($fsize == 0)
{
header('Location: #'); // this doesn't work!!! (too many redirectcts)
exit;
}
//$dlname = $path_parts['filename'] . "." . strtolower($path_parts["extension"]);
header("Cache-Control: public");
header("Content-Description: File Transfer");
header("Content-Disposition: filename=\"" . $path_parts["basename"]."\"");
header("Content-Type: application/x-file-to-save");
header("Content-Transfer-Encoding: binary");
if($fsize) header("Content-length: $fsize");
$bytesRead = readfile($path);
return $bytesRead;
}
If you are using HTTP/1.x with a standard anchor tag, without JavaScript or other client-side interception. An HTTP/1.0 204 No Content status header will cause the user-agent to simply seem like nothing happened when clicking a link that returns a 204 status header.
HTTP/1.0 204 No Content
The server has fulfilled the request but there is no new information
to send back. If the client is a user agent, it should not change its
document view from that which caused the request to be generated. This
response is primarily intended to allow input for scripts or other
actions to take place without causing a change to the user agent's
active document view. The response may include new metainformation in
the form of entity headers, which should apply to the document
currently in the user agent's active view.
Source: https://www.w3.org/Protocols/HTTP/1.0/spec.html#Code204
This is also compatible with the HTTP/1.1 protocol.
I recommend using output buffering to ensure no other content is being sent by your application by mistake. Additionally there should be no need to send a Content-Length header.
function downloadFile($path) {
if (!is_file($path) || !($fsize = filesize($path))) {
header('HTTP/1.0 204 No Content');
exit;
}
$path_parts = pathinfo($path);
header('Cache-Control: public');
header('Content-Description: File Transfer');
header('Content-Disposition: filename="' . $path_parts['basename'] . '"');
header('Content-Type: application/x-file-to-save');
header('Content-Transfer-Encoding: binary');
header('Content-length: ' . $fsize); //fsize already validated above.
return readfile($path);
}
Performing the file checks before creating the links is the simplest way to do this.
If I understand your request correctly you have files that you wish to allow a client to download, and links to PHP scripts that download certain files.
The problem with your implementation is that when the file is empty, the PHP script still must load and change the content of the clients page(from the action of loading the script), which is the incorrect behavior (correct being no action at all).
Since you are using tags on the main download page, really the only way to not change the content of the page in the case of a missing file is to compute the content of the tags in advance. With a simple PHP function you could check the contents of a list of files and their directories, and then generate links for the ones that exist, and blank links for the ones that do not.
Overall, I think separating the functionality of checking whether a file exists and actually downloading the file to a client is the only way to allow the functionality you desire.
I have a very basic question illustrated by the code snippet below.
This is the relevant part of a much bigger program in which I wish to download a zip file. The code as shown, with the comments in place, produce the expected browser output "Download the file now."
When I un-comment the code, the zip file is correctly downloaded to my browser!
However, the browser output is not produced. How do I regain control? I would like for the user to then have other options. (By the way, un-commenting the single "Content-disposition" line is sufficient to cause the loss of control.)
I have tried including the code, putting it in a function, many possible combinations of ob_start, ob_end flush, etc., all to no avail. I am sure I am overlooking something very fundamental and would appreciate some suggestions.
Thanks.
<?php
$sZipFN = 'file.zip';
// header("Content-type: application/zip");
// header("Content-disposition: attachment; filename=$sZipFN");
// readfile($sZipFN);
$sMsg = "Download the file now.";
?>
<html>
<body>
<p> <?php echo $sMsg; ?> </p>
</body>
</html>
You can't - you have to redirect to the options page and then start the download via javascript redirect (document.location = 'http://download.url/';)
This will start the download and leave the user on the options page like you desire.
Don't forget to include a 'Click here if the download fails to start' link somewhere near the top of the page (just in case javascript is disabled)
My intention is to convert a total php page into html, and subsequently convert the html to pdf and render it through the browser.Which is done , apart from that while showing it on the browser , it will simultaneously download the pdf automatically which is not happening.
Its with PHP.
Can to tell me the basic concept ..as to how to do this.
Thanks in advance
You already render the page in the browser. Before displaying the page, header() the user to the location which will serve the same page as an attachment, but do not exit. This will allow them to download the file, but it will still load the file on the page. Not 100% sure that this will work, but it's worth a shot.
BTW different browsers will handle pdfs differently and depending on settings, plugins, etc. For instance, some might try to download the file anyway instead of showing it in the browser.
I think you need to look over the question again. As I read it, you're asking how to display something that hasn't yet been downloaded (while it's downloading), and that is obviously not possible and so cannot be what you mean.
Try creating a header, which tells the browser what to do when it receives the file.
<?php
header("Content-Type: $filedatatype" );
header("Content-Disposition: attachment; filename=\"" . $FileObject->name . "\";");
header("Content-Transfer-Encoding: binary");
header("Content-Length: " . $filesize);
?>
I'm trying to accomplish a fairly simple task for my website, but I"m not sure exactly how to go about it. I want the user to be viewing a table, then click a button, at which point the user can save the contents of that table as a csv file. This request can sometimes be quite complicated so I generate a progress page to alert the user.
I have most things figured out except actually generating the csv file. (I use jQuery and PHP)
the jQuery code run on click:
hmis_query_csv_export: function(query_name) {
$.uiLock('<p>Query Loading.</p><img src="/images/loading.gif" />')
$.get({
url: '/php_scripts/utils/csv_export.php',
data: {query_name: query_name},
success: function(data) {
$.uiUnlock();
}
});}
the relevant PHP:
header("Content-type: text/x-csv");
header("Content-Disposition: attachment; filename=search_results.csv");
//
//Generate csv
//
echo $csvOutput
exit();
What this does is sends the text as the PHP file, but it's doesn't generate a download. What am I doing wrong?
If you are forcing a download, you can redirect the current page to the download link. Since the link will generate a download dialog, the current page (and its state) will be kept in place.
Basic approach:
$('a#query_name').click(function(){
$('#wait-animation').show();
document.location.href = '/php_scripts/utils/csv_export.php?query_name='+query_name;
$('#wait-animation').hide();
});
More complicated:
$('a#query_name').click(function(){
MyTimestamp = new Date().getTime(); // Meant to be global var
$('#wait-animation').show();
$.get('/php_scripts/utils/csv_export.php','timestamp='+MyTimestamp+'&query_name='query_name,function(){
document.location.href = '/php_scripts/utils/csv_export.php?timestamp='+MyTimestamp+'&query_name='+query_name;
$('#wait-animation').hide();
});
});
At PHP script:
#header("Last-Modified: " . #gmdate("D, d M Y H:i:s",$_GET['timestamp']) . " GMT");
#header("Content-type: text/x-csv");
// If the file is NOT requested via AJAX, force-download
if(!isset($_SERVER['HTTP_X_REQUESTED_WITH']) || strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) != 'xmlhttprequest') {
header("Content-Disposition: attachment; filename=search_results.csv");
}
//
//Generate csv
//
echo $csvOutput
exit();
The URL for both requests must be the same to trick the browser not to start a new download at document.location.href, but to save the copy at the cache. I'm not totally sure about it, but seems pretty promising.
EDIT I just tried this with a 10MB file and it seems that val() is too slow to insert the data. Hurrumph.
Okay, so I gave this one another go. This may or may not be completely insane! The idea is to make an AJAX request to create the data, then use the callback to insert the data into a hidden form on the current page which has an action of a third "download" page; after the insertion, the form is automatically submitted, the download page sends headers and echoes the POST, and et voila, download.
All the while, on the original page you've got an indication that the file is being prepared, and when it finishes the indicator is updated.
NOTE: this test code isn't tested extensively, and has no real security checks (or any at all) put in place. I tested it with a 1.5MB CSV file I had laying about and it was reasonably snappy.
Index.html
<a id="downloadlink" href="#">Click Me</a>
<div id="wait"></div>
<form id="hiddenform" method="POST" action="download.php">
<input type="hidden" id="filedata" name="data" value="">
</form>
test.js
$(document).ready(function(){
$("#downloadlink").click(function(){ // click the link to download
lock(); // start indicator
$.get("create.php",function(filedata){ // AJAX call returns with CSV file data
$("#filedata").val(filedata); // insert into the hidden form
unlock(); // update indicator
$("#hiddenform").submit(); // submit the form data to the download page
});
});
function lock(){
$("#wait").text("Creating File...");
}
function unlock(){
$("#wait").text("Done");
}
});
create.php
<?php
//create $data
print $data;
?>
download.php
<?php
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Content-Type: text/x-csv");
header("Content-Disposition: attachment;filename=\"search_results.csv\"");
if($_POST['data']){
print $_POST['data'];
}
?>
The best way to accomplish this is to use a Data URI as follows:
Make the AJAX call to the server as per normal
Generate the CSV on the server-side
Return the data (either bare or inside a JSON structure)
Create a Data URI in Javascript using the returned data
Set window.location.href to the Data URI
See this link for instructions (paragraph #3, specifically): http://en.wikipedia.org/wiki/Data_URI_scheme
This way, you don't need to save any files on the server, and you also don't need to use iframes or hidden form elements or any such hacks.
I don't think you can make the browser download using a AJAX/JS request. Try using a hidden iframe that navigates to the page which generates the CSV
Well the point of using AJAX is to avoid a visible reload of the page. If you want a download, you want the opposite,- a brand new request from the browser. I'd say, just create a simple button pointing to your php page.
To echo and expand on what others have said, you can't really send the file using AJAX. One of the reasons for this is (and someone correct me if I'm wrong on this, please) that the page you're currently on already has sent its content headers; you can't send them again to the same window, even with an AJAX request (which is what your PHP file is attempting to do).
What I've done before in projects is to simply provide a link (with target="_blank" or javascript redirect) to a separate download PHP page. If you're using Apache, check out mod_xsendfile as well.
On a PHP-based web site, I want to send users a download package after they have filled out a short form. The site-initiated download should be similar to sites like download.com, which say "your download will begin in a moment."
A couple of possible approaches I know about, and browser compatibility (based on a quick test):
1) Do a window.open pointing to the new file.
- FireFox 3 blocks this.
- IE6 blocks this.
- IE7 blocks this.
2) Create an iframe pointing to the new file.
- FireFox 3 seems to think this is OK. (Maybe it's because I already accepted it once?)
- IE6 blocks this.
- IE7 blocks this.
How can I do this so that at least these three browsers will not object?
Bonus: is there a method that doesn't require browser-conditional statements?
(I believe that download.com employs both methods conditionally, but I can't get either one to work.)
Responses and Clarifications:
Q: "Why not point the current window to the file?"
A: That might work, but in this particular case, I want to show them some other content while their download starts - for example, "would you like to donate to this project?"
UPDATE: I have abandoned this approach. See my answer below for reasons.
You can also do a meta refresh, which most browsers support. Download.com places one in a noscript tag.
<meta http-equiv="refresh" content="5;url=/download.php?doc=123.zip"/>
Update: I have decided to abandon this approach, and instead just present the user with a link to the actual file. My reasoning is this:
My initial attempts at a server-initiated download were blocked by the browser. That got me thinking: "the browser is right. How does it know that this is a legitimate download? It should block a download that isn't obviously user-initiated."
Any method that I can use for a server-initiated download could also be used by someone who wants to send malware. Therefore, downloads should only happen when the user specifically requests the file by clicking on a link for it.
You're free to disagree, and if you still want to initiate a download, hopefully this thread will help you do it.
I usually just have a PHP script that outputs the file directly to the browser with the appropriate Content-Type
if(file_exists($filename)) {
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, pre-check=0");
header("Cache-Control: private", false);
header("Content-Type: " . $content-type);
header("Content-Disposition: attachment; filename=\"" . basename($filename) . "\";" );
header("Content-Transfer-Encoding: binary");
header("Content-Length: " . filesize($filename));
readfile("$filename");
}else{
print "ERROR: the file " . basename($filename) . " could not be downloaded because it did not exist.";
}
The only disadvantage is that, since this sets the HTTP header, it has be called before you have any other output.
But you can have a link to the PHP download page and it will cause the browser to pop up a download box without messing up the content of the current page.
One catch is that you may encounter issues with IE (version 6 in particular) if the headers are not set up "correctly".
Ensure you set the right Content-Type, but also consider setting the Cache options for IE (at least) to allow caching. If the file is one the user can open rather than save (e.g. an MS Word document) early versions of IE need to cache the file, as they hand off the "open" request to the applicable app, pointing to the file that was downloaded in the cache.
There's also a related issue, if the IE6 user's cache is full, it won't properly save the file (thus when the applicable app gets the hand off to open it, it will complain the file is corrupt.
You may also want to turn of any gzip actions on the downloads too (for IE)
IE6/IE7 both have issues with large downloads (e.g. 4.x Gigs...) not a likely scenario since IE doesn't even have a download manager, but something to be aware of.
Finally, IE6 sometimes doesn't nicely handle a download "push" if it was initiated from within a nested iframe. I'm not exactly sure what triggers the issue, but I find it is easier with IE6 to avoid this scenario.
Hoi!
#Nathan:
I decided to do exactly that: Have my "getfile.php" load all necessary stuff and then do a
header("Location: ./$path/$filename");
to let the browser itself and directly do whatever it thinks is correct do with the file. This even works fine in Opera with me.
But this will be a problem in environments, where no direct access to the files is allowed, in that case you will have to find a different way! (Thank Discordia my files are public PDFs!)
Best regards, Basty
How about changing the location to point to the new file? (e.g. by changing window.location)
I've always just made an iframe which points to the file.
<iframe src="/download.exe" frameborder="0" height="0" width="0">Click here to download.</iframe>
Regarding not pointing the current window to the download.
In my experience you can still show your "please donate" page, since downloads (as long as they send the correct headers) don't actually update the browser window.
I do this for csv exports on one of my sites, and as far as the user is concerned it just pops up a safe file window.
So i would recommend a simple meta-redirect as Soldarnal showed.
Just to summarise, you have 2 goals:
start download process
show user a page with a donate options
To achieve this I would do the following:
When your user submits the form, he gets the resulting page with a donate options and a text saying that his download will start in 5 seconds. And in the head section of this page you put the META code as Soldarnal said:
<meta http-equiv="refresh" content="5;url=/download.php?doc=123.zip>
And that's all.
<a href="normaldownload.zip" onclick="use_dhtml_or_ajax_to_display_page()">
Current page is unaffected if download is saved. Just ensure that download doesn't open in the same window (proper MIME type or Content-Disposition) and you'll be able to show anything.
See more complete answer
You can use Javascript/jQuery to initiate the download. Here's an example - you can get rid of the Ajax request and just use the setTimeout() block.
$("btnDownloadCSV").on('click', function() {
$.ajax({
url: "php_backend/get_download_url",
type: 'post',
contentType: "application/x-www-form-urlencoded",
data: {somedata: "somedata"},
success: function(data) {
// If iFrame already exists, remove it.
if($("[id^='iframeTempCSV_"]).length) {
$("[id^='iframeTempCSV_"]).remove();
}
setTimeout(function() {
// If I'm creating an iframe with the same id, it will permit download only the first time.
// So randHashId appended to ID to trick the browser.
var randHashId = Math.random().toString(36).substr(2);
// Create a fresh iFrame for auto-downloading CSV
$('<iframe id="iframeTempCSV_'+randHashId+'" style="display:none;" src="'+data.filepath+'"></iframe>').appendTo('body');
}, 1000);
},
error: function(xhr, textStatus, errorThrown) {
console.error("Error downloading...");
}
});
});