When a user clicks a submit button I want the form to be submitted. However, just before this happens, I want a window to pop open and for them to fill in some data. Once they do this and they close that child window, I want the POST request to be made.
Is this possible, if so how? I just need help after the window closes, how can I make that POST request continue?
Thanks all
Couldn't you just add a
onunload=parent.form.submit()?
http://www.w3schools.com/jsref/jsref_onunload.asp
You can do something like this.. (note the code is simplified and you can probably structure it better)
This is in your main document with the form:
var childFilled = false;
myForm.onsubmit = function() {
if(!childFilled) {
window.open(...);
return false;
}
};
function submitFormFromChild() {
childFilled = true;
myForm.submit();
}
And in the window's code you have something like this:
window.onunload = parent.submitFormFromChild;
Untested, unproven, but the general concept is something like this =)
To be clear: you meant to ask (and asked in the question) how to intercept form-submission in the browser.
The title of your post implies that you are asking how to perform an asynchronous HTTP POST operation, do something else, and subsequently wait for that HTTP POST operation to complete. That whole process is not necessarily related to user interaction and is not necessarily related to HTML form submission, and it is not the same thing at all as what you meant to ask (and asked in the question).
Related
I have read many similar questions concerning cancelling a POST request with jQuery, but none seem to be close to mine.
I have your everyday form that has a PHP-page as an action:
<form action="results.php">
<input name="my-input" type="text">
<input type="submit" value="submit">
</form>
Processing results.php on the server-side, based on the post information given in the form, takes a long time (30 seconds or even more and we expect an increase because our search space will increase as well in the coming weeks). We are accessing a Basex server (version 7.9, not upgradable) that contains all the data. A user-generated XPath code is submitted in a form, and the action url then sends the XPath code to the Basex server which returns the results. From a usability perspective, I already show a "loading" screen so users at least know that the results are being generated:
$("form").submit(function() {
$("#overlay").show();
});
<div id="overlay"><p>Results are being generated</p></div>
However, I would also want to give users the option to press a button to cancel the request and cancel the request when a user closes the page. Note that in the former case (on button click) this also means that the user should stay on the same page, can edit their input, and immediately re-submit their request. It is paramount that when they cancel the request, they can also immediately resend it: the server should really abort, and not finish the query before being able to process a new query.
I figured something like this:
$("form").submit(function() {
$("#overlay").show();
});
$("#overlay button").click(abortRequest);
$(window).unload(abortRequest);
function abortRequest() {
// abort correct request
}
<div id="overlay">
<p>Results are being generated</p>
<button>Cancel</button>
</div>
But as you can see, I am not entirely sure how to fill in abortRequest to make sure the post request is aborted, and terminated, so that a new query can be sent. Please fill in the blanks! Or would I need to .preventDefault() the form submission and instead do an ajax() call from jQuery?
As I said I also want to stop the process server-side, and from what I read I need exit() for this. But how can I exit another PHP function? For example, let's say that in results.php I have a processing script and I need to exit that script, would I do something like this?
<?php
if (isset($_POST['my-input'])) {
$input = $_POST['my-input'];
function processData() {
// A lot of processing
}
processData()
}
if (isset($_POST['terminate'])) {
function terminateProcess() {
// exit processData()
}
}
and then do a new ajax request when I need to terminate the process?
$("#overlay button").click(abortRequest);
$(window).unload(abortRequest);
function abortRequest() {
$.ajax({
url: 'results.php',
data: {terminate: true},
type: 'post',
success: function() {alert("terminated");});
});
}
I did some more research and I found this answer. It mentions connection_aborted() and also session_write_close() and I'm not entirely sure which is useful for me. I do use SESSION variables, but I don't need to write away values when the process is cancelled (though I would like to keep the SESSION variables active).
Would this be the way? And if so, how do I make one PHP function terminate the other?
I have also read into Websockets and it seems something that could work, but I don't like the hassle of setting up a Websocket server as this would require me to contact our IT guy who requires extensive testing on new packages. I'd rather keep it to PHP and JS, without third party libraries other than jQuery.
Considering most comments and answers suggest that what I want is not possible, I am also interested to hear alternatives. The first thing that comes to mind is paged Ajax calls (similar to many web pages that serve search results, images, what-have-you in an infinite scroll). A user is served a page with the X first results (e.g. 20), and when they click a button "show next 20 results" those are shown are appended. This process can continue until all results are shown. Because it is useful for users to get all results, I will also provide a "download all results" option. This will then take very long as well, but at least users should be able to go through the first results on the page itself. (The download button should thus not disrupt the Ajax paged loads.) It's just an idea, but I hope it gives some of you some inspiration.
On my understanding the key points are:
You cannot cancel a specific request if a form is submitted. Reasons are on client side you don't have anything so that you can identify the states of a form request (if it is posted, if it is processing, etc.). So only way to cancel it is to reset the $_POST variables and/or refresh the page. So connection will be broken and the previous request will not be completed.
On your alternative solution when you are sending another Ajax call with {terminate: true} the result.php can stop processing with a simple die(). But as it will be an async call -- you cannot map it with the previous form submit. So this will not practically work.
Probable solution: submit the form with Ajax. With jQuery ajax you will have an xhr object which you can abort() upon window unload.
UPDATE (upon the comment):
A synchronous request is when your page will block (all user actions) until the result is ready. Pressing a submit button in the form - do a synchronous call to server by submitting the form - by definition [https://www.w3.org/TR/html-markup/button.submit.html].
Now when user has pressed submit button the connection from browser to server is synchronous - so it will not be hampered until the result is there. So when other calls to server is made - during the submit process is going on - no reference of this operation is available for others - as it is not finished. It is the reason why sending termination call with Ajax will not work.
Thirdly: for your case you can consider the following code example:
HTML:
<form action="results.php">
<input name="my-input" type="text">
<input id="resultMaker" type="button" value="submit">
</form>
<div id="overlay">
<p>Results are being generated</p>
<button>Cancel</button>
</div>
JQUERY:
<script type="text/javascript">
var jqXhr = '';
$('#resultMaker').on('click', function(){
$("#overlay").show();
jqXhr = $.ajax({
url: 'results.php',
data: $('form').serialize(),
type: 'post',
success: function() {
$("#overlay").hide();
});
});
});
var abortRequest = function(){
if (jqXhr != '') {
jqXhr.abort();
}
};
$("#overlay button").on('click', abortRequest);
window.addEventListener('unload', abortRequest);
</script>
This is example code - i just have used your code examples and changed something here and there.
Himel Nag Rana demonstrated how to cancel a pending Ajax request.
Several factors may interfere and delay subsequent requests, as I have discussed earlier in another post.
TL;DR: 1. it is very inconvenient to try to detect the request was cancelled from within the long-running task itself and 2. as a workaround you should close the session (session_write_close()) as early as possible in your long-running task so as to not block subsequent requests.
connection_aborted() cannot be used. This function is supposed to be called periodically during a long task (typically, inside a loop). Unfortunately there is just one single significant, atomic operation in your case: the query to the data back end.
If you applied the procedures advised by Himel Nag Rana and myself, you should now be able to cancel the Ajax request and immediately allow a new requests to proceed. The only concern that remains is that the previous (cancelled) request may keep running in the background for a while (not blocking the user, just wasting resources on the server).
The problem could be rephrased to "how to abort a specific process from the outside".
As Christian Bonato rightfully advised, here is a possible implementation. For the sake of the demonstration I will rely on Symphony's Process component, but you can devise a simpler custom solution if you prefer.
The basic approach is:
Spawn a new process to run the query, save the PID in session. Wait for it to complete, then return the result to the client
If the client aborts, it signals the server to just kill the process.
<?php // query.php
use Symfony\Component\Process\PhpProcess;
session_start();
if(isset($_SESSION['queryPID'])) {
// A query is already running for this session
// As this should never happen, you may want to raise an error instead
// of just silently killing the previous query.
posix_kill($_SESSION['queryPID'], SIGKILL);
unset($_SESSION['queryPID']);
}
$queryString = parseRequest($_POST);
$process = new PhpProcess(sprintf(
'<?php $result = runQuery(%s); echo fetchResult($result);',
$queryString
));
$process->start();
$_SESSION['queryPID'] = $process->getPid();
session_write_close();
$process->wait();
$result = $process->getOutput();
echo formatResponse($result);
?>
<?php // abort.php
session_start();
if(isset($_SESSION['queryPID'])) {
$pid = $_SESSION['queryPID'];
posix_kill($pid, SIGKILL);
unset($pid);
echo "Query $pid has been aborted";
} else {
// there is nothing to abort, send a HTTP error code
header($_SERVER['SERVER_PROTOCOL'] . ' 599 No pending query', true, 599);
}
?>
// javascript
function abortRequest(pendingXHRRequest) {
pendingXHRRequest.abort();
$.ajax({
url: 'abort.php',
success: function() { alert("terminated"); });
});
}
Spawning a process and keeping track of it is genuinely tricky, this is why I advised using existing modules. Integrating just one Symfony component should be relatively easy via Composer: first install Composer, then the Process component (composer require symfony/process).
A manual implementation could look like this (beware, this is untested, incomplete and possibly unstable, but I trust you will get the idea):
<?php // query.php
session_start();
$queryString = parseRequest($_POST); // $queryString should be escaped via escapeshellarg()
$processHandler = popen("/path/to/php-cli/php asyncQuery.php $queryString", 'r');
// fetch the first line of output, PID expected
$pid = fgets($processHandler);
$_SESSION['queryPID'] = $pid;
session_write_close();
// fetch the rest of the output
while($line = fgets($processHandler)) {
echo $line; // or save this line for further processing, e.g. through json_encode()
}
fclose($processHandler);
?>
<?php // asyncQuery.php
// echo the current PID
echo getmypid() . PHP_EOL;
// then execute the query and echo the result
$result = runQuery($argv[1]);
echo fetchResult($result);
?>
With BaseX 8.4, a new RESTXQ annotation %rest:single was introduced, which allows you to cancel a running server-side request: http://docs.basex.org/wiki/RESTXQ#Query_Execution. It should solve at least some of the challenges you described.
The current way to only return chunks of the result is to pass on the index to the first and last result in your result, and to do the filtering in XQuery:
$results[position() = $start to $end]
By returning one more result than requested, the client will know that there will be more results. This may be helpful, because computing the total result size is often much more expensive than returning only the first results.
I hope I understood this correctly.
Instead of letting the browser "natively" submit the FORM, don't: write JS code that does this instead. In other words (I didn't test this; so interpret as pseudo-code):
<form action="results.php" onsubmit="return false;">
<input name="my-input" type="text">
<input type="submit" value="submit">
</form>
So, now, when the that "submit" button is clicked, nothing will happen.
Obviously, you want your form POSTed, so write JS to attach a click handler on that submit button, collect values from all input fields in the form (actually, it is NOT nearly as scary as it sounds; check out the link below), and send it to the server, while saving the reference to the request (check the 2nd link below), so that you can abort it (and maybe signal the server to quit also) when the cancel-button is clicked (alternatively, you can simply abandon it, by not caring about the results).
Submit a form using jQuery
Abort Ajax requests using jQuery
Alternatively, to make that HTML markup "clearer" relative to its functionality, consider not using FORM tag at all: otherwise, what I suggested makes its usage confusing (why it is there if it's not used; know I mean?). But, don't get distracted with this suggestion until you make it work the way you want; it's optional and a topic for another day (it might even relate to your changing architecture of the whole site).
HOWEVER, a thing to think about: what to do if the form-post already reached the server and server already started processing it and some "world" changes have already been made? Maybe your get-results routine doesn't change data, so then that's fine. But, this approach probably cannot be used with change-data POSTs with the expectation that "world" won't change if cancel-button is clicked.
I hope that helps :)
The user doesn't have to experience this synchronously.
Client posts a request
The server receives the client request and assigns an ID to it
The server "kicks off" the search and responds with a zero-data page and search ID
The client receives the "placeholder" page and starts checking if the results are ready based on the ID (with something like polling or websockets)
Once the search has completed, the server responds with the results next time it's polled (or notifies the client directly when using websockets)
This is fine when performance isn't quite the bottleneck and the nature of processing makes longer wait times acceptable. Think flight search aggregators that routinely run for 30-90 seconds, or report generators that have to be scheduled and run for even longer!
You can make the experience less frustrating if you don't block user interactions, keep them updated of search progress and start showing results as they come in if possible.
You must solve this conceptually first before writing any code. Here are some things that come to mind offhand:
What does it mean to free up resources on the server?
What constitutes to a graceful abort that will free up resources?
Is it enough to kill the PHP process waiting for the query result(s)? If so, the route suggested by RandomSeed could be interesting. Just keep in mind that it will only work on a single server. If you have multiple load balanced servers you won't have a way to kill a process on another server (not as easily at least).
Or do you need to cancel the database request from the database itself? In that case the answer suggested by Christian Grün is of more interest.
Or is it that there is no graceful shutdown and you have to force everything to die? If so, this seems awfully hacky.
Not all clients are going to explicitly abort
Some clients are going to close the browser, but their last request won't come through; some clients will lose internet connection and leave the service hanging, etc. You are not guaranteed to get an "abort" request when a client disconnects or has gone away.
You have to decide whether to live with potentially unwanted behavior, or implement an additional active state tracking, e.g. client pinging server for keepalive.
Side notes
30 secs or greater query time is potentially long, is there a better tool for the job; so you won't have to solve this with a hack like this?
you are looking for features of a concurrent system, but you're not using a concurrent system; if you want concurrency use a better tool/environment for it, e.g. Erlang.
Firstly, sorry for my bad English (I'm Italian).
Anyway, I'm making a web-site project for school, so I'm using HTML, CSS and PHP languages.
I'd like to put a sort of button-link (for example the "Like" one, as in Facebook) but how can I do it?
In Facebook, when I click on "Like", I won't be redirected to another page, so it can't be something like:
Like
In fact, I want the user to be in the same page at the same position
I thought I could write something like this (I'll call this file home.php):
<a name="5">
<a href="like.php?position=5&user=Paul>Like</a>
So, I will write in PHP something like:
<?php
// Database connection
// Adding a like in database. The user who liked the object is in $_GET['user']
// ...
header("location:home.php#$_GET[position]");
?>
But I don't want the user to be redirected to a page call like.php which redirect, in turn, the user at the beginning page...
How can I do it? And how can I connect to database?
Thanks in advance ^^
I can't provide code because what you're asking is too much. All I can do is steer you the right way to get your answers.
You're asking how to do at least 3 different things here that all require an explanation. So look up the following, and how they function:
AJAX. This will let your page send a message (like a button click to a PHP page).
PHP. You will need this to intercept the message and return the result.
MySQL. You will need this to create a table, hold your data, modify your data, and retrieve data to respond back to your main page.
Here is a simple example:
HTML graphic for buttonbutton
<img src="button.png" alt="playButton" border="0" onclick="countClick('1','Google')">
Javascript for the AJAX
function countClick(id,host) {
var xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (xhttp.readyState == 4 && xhttp.status == 200) {
//document.getElementById("demo").innerHTML = xhttp.responseText;
}
};
xhttp.open("GET", "/includes/appCounter.php?appid="+ id +"&hostIs="+ host, true);
xhttp.send();
}
What this does is, when the user clicks the button, it goes to whatever link is there. But it also triggers the "onclick". This fires the Javascript.
The Javascript function makes a simple AJAX call to the server, passing in an ID and a Host. The PHP page knows what to do with those parameters.
In this case, there isn't any need for the page to even care about the response.
It happens in the background. In the end, a counter in my database is updated to let me know they clicked that button.
In the real world, it looks like this: http://android.dpoisn.com/
I want to do something like this: If I am viewing a record and edit it or add a new record and then exit that screen, I should be asked, “Do you want to save?”
How can I develop this thing in php? I haven't done this type of development before..
Any suggestions?
use jquery onbeforeunload function it will be execute when page refresh or
closing browser tab or closing browser .
$(window).on('beforeunload', function(){
return 'Are you sure you want to leave?';
});
You need to look for changes in javascript. Make a global variable, lets call it changed . Set it to false on page load. Whenever record is edited make it true and whenever it is saved , set it to false. When the user is closing his tab, again which needs to be detected in JS, look for changed variable. If it is true give him a prompt else he can close without any issues.
You will need to javascipt/jquery to listen for the unload event on the window.
I believe you could do something along the lines of:
<script>
function saveAlert() {
var confirm = confirm('You haven\'t saved your form! Do you want to save?');
if (confirm) {
$('form').submit();
}
return confirm;
}
$(function() {
var formSaved = <?=($formSaved) ? 'true' : 'false'?>;
if (!formSaved) {
$( window ).unload(saveAlert());
}
});
All you will need to do is pass a boolean in the $formSaved variable to determine whether the alert needs to be shown or not.
If you wanted to attempt a solution to this question in PHP, you would need to use AJAX to store field data in the database on change/update of fields, without committing the change to the table - you could store it in a cookie or session variable, or in an 'unsaved_records' table of some sort.
If your user navigates to an off-site domain there's nothing you can do in PHP but if they come back to your site, you can alert "you have unsaved data, do you want to continue where you left off?".
You could also wait till they return to the page where they had unsaved data, and restore it to the state it was in, as though they had never left. This would require some careful planning, but it's possible.
Only client side scripting can pause the window or tab being directed to a new location, as is evident in the other answers here.
I am trying to make a chat room on my website, I am using php and mysql to store the messages and all the info. How could I automatically refresh the page every time someone updates the database? example:
If I am on my site, the messages show up on my screen but I can only see more recent messages after I refresh the page. Is there a way to make it real-time?
Also I do not know much javascript/ajax/jquery or any of that. Any help is appreciated!
There will be low amount of traffic on my site. Probably around 10-15 people at a time, if that even.
Your best bet is to make an AJAX request every sec or so and see if there are new messages.
You probably do not want to be reloading the page every time. My recommendation, and there are many ways to do this, is to make a ajax call every so often and check/pull the new information from the database.
I would research AJAX and do a tutorial.
This would be accomplished through ajax by calling a function and updating the div. I would not suggest making people refresh a page everytime they send a message it would get ugly. Another option would be using HTML5 web workers
http://msdn.microsoft.com/en-us/hh549259.aspx
You are going to need to learn AJAX in order to make this work well, and jQuery is probably the easiest way to do it. If we can assume that the DIV you want to update has the ID PonyRides, you would want to do:
$("#PonyRides").ajax({url: "/chat.php?getupdates=true"});
This will get the contents of chat.php and stick it into the #PonyRides DIV. This assumes that chat.php will get the contents of the database and format them into HTML.
The remaining challenge is to make it update whenever your database does, but the simplest way is just to reload the whole chat regardless of whether an update has been made or not.
That will impact performance, but if you have less than a hundred chatters you'll probably be fine. If you have more than that, you'd do well to sense inactivity and decrease the checking period, or only send updates instead of the whole chat. Those are more complicated topics, though, and you can build them in as needed once you get these basic concepts down.
To do this, simply wrap the ajax() call in an interval like so:
setInterval(function(){ //the following code runs repeatedly
$("#PonyRides").ajax({url: "/chat.php?getupdates=true"}); //update our chat div
},5000); //repeat every five seconds
The other, awful method would be to load chat in an iFrame, set to reload periodically using the meta refresh technique. This would be dreadful, and can only be recommended if you are trying for some reason to support incredibly old browsers.
You can use AJAX request to update the values
<script type='text/javascript'>
// function for making an object for making AJAX request
function getXMLHTTPRequest() {
try {
req = new XMLHttpRequest();
} catch(err1) {
try {
req = new ActiveXObject("Msxml2.XMLHTTP");
} catch (err2) {
try {
req = new ActiveXObject("Microsoft.XMLHTTP");
} catch (err3) {
req = false;
}
}
}
return req;
}
var http899 = getXMLHTTPRequest();
function searchFabIndia() {
var myurl = "http://my2nddomain.com/yebhi.php";
myRand = parseInt(Math.random()*999999999999999);
var modurl = myurl+"?rand="+myRand;
http899.open("GET", modurl, true);
http899.onreadystatechange = useHttpResponse899;
http899.send(null);
}
function useHttpResponse899() {
if (http899.readyState == 4) {
if(http899.status == 200) {
// do all processings with the obtained values / response here
// after doing the stuff, call fn again after 30 s say
setTimeout("searchFabIndia()", 30000);
}
}
}
</script>
<body onload='searchFabIndia();'>
I would suggest making an AJAX request to a file on your server which will update the database. If the update to the database is successful then return the message which was updated. Back on the client side you wait for the response and if you get one then append the message to the end of the content. This way you're loading all the messages every time (which would be expensive), you're only loading new messages.
There must be something similar to SignalR(.net) for php. It lets you add code when an event occurs, I think that is what you are looking for.
I have a page on which I want to show a couple of MySQL tables.
There is one table on the right that may only change when a different person is selected.
De second table is the main table in the center. I have a dropdown box with contains every person. The results from the selected person is showed in the middle table. There are multiple results for each person so there is a second dropdown box to choose which of these results you want to show. This is al done by a Ajax XMLHTTP request.
The problem is that the right table uses some javascript. I know this is not possible with Ajax in combination with a XMLHTTP-request. But without the javascript I can't make what I want. Is there a way, to show the right table after the javascript is finished doing his work?
I now use frames. This is not very nice. Because I have to style both pages to look nice together, and that's not so easy as said. But this way it is doing as I want it to be.
So I searched the internet (a long time) and just a few minutes before I wanted to give up i found this piece of code (coming from http://www.javascriptkit.com/dhtmltutors/ajaxincludes.shtml):
function HttpRequest(url){
var pageRequest = false //variable to hold ajax object
/*#cc_on
#if (#_jscript_version >= 5)
try {
pageRequest = new ActiveXObject("Msxml2.XMLHTTP")
}
catch (e){
try {
pageRequest = new ActiveXObject("Microsoft.XMLHTTP")
}
catch (e2){
pageRequest = false
}
}
#end
#*/
if (!pageRequest && typeof XMLHttpRequest != 'undefined')
pageRequest = new XMLHttpRequest()
if (pageRequest){ //if pageRequest is not false
pageRequest.open('GET', url, false) //get page synchronously
pageRequest.send(null)
embedpage(pageRequest)
}
}
function embedpage(request){
//if viewing page offline or the document was successfully retrieved online (status code=2000)
if (window.location.href.indexOf("http")==-1 || request.status==200)
document.write(request.responseText)
}
}
HttpRequest("external.htm") //include "external.htm" onto current page
This code works perfectly... The first time. As soon as you change the person the whole page disappears and only the table shows up and firefox keeps "loading" the page (you see that circle going round). I do know how to edit the code above to fit my needs but I have no understanding of Ajax or how to fix this problem. Hopefully someone can help me and give me a good solution! And tell me why the code above isn't working properly?
Thanks in advance!
Milaan
document.write only works when the page is loading for the first time, Once the page rendering is done, calling document.write will clear the page first.
https://developer.mozilla.org/en/document.write
What you might want to do instead is:
if (window.location.href.indexOf("http")==-1 || request.status==200) {
var elm = document.createElement('div');
elm.innerHTML = request.responseText;
document.getElementsByTagName('body')[0].appendChild(elm);
}
It´s been a long time since I´ve seen code like this, but one problem I can see, is that you don´t include any kind of variable in your XMLHttpRequest; no user ID or anything. Is it just supposed to load a static page?
And is there any reason you can´t use a library like jQuery? It´s no magic bullet but it will make your life and ajax requests a lot easier.
You might want to use dom functions to add your downloaded content to the existing document, like:
document.getElementById('mypanel').innerHTML = '<html code goes here>';
The best idea probably would be to use a slim javascript framework lie jquery which helps you with browser compatibility.
jQuery should make things easier for you. Your code should look something like this.
$.post("somepage.php", function(data){
$("#divID").html(data);
});
<div id="divID"></div>
And somepage.php could be something like this:
<?php
// get table content
echo "<table>...</table>";
?>