Let's assume PHPFile.php return random integer(X) every 2 seconds.
Now if X == 5 I would like to show an alert (client-side).
the following code will do that job :
$(function worker(){
$.ajaxSetup ({
cache: false,
complete: function() {
// Schedule the next request when the current one's complete
setTimeout(worker, 2000);
}
});
$.ajax({
type: "GET",
url: "PHPFile.php",
success:function(result){
if (result == 5){
alert('test');
}
};
});
Now the problem is when we call this every 2 seconds it's like destroying the memory, especially if PHPFile.php(in example) has big size data.
30 Request every one minute and its counting.
So I wondering what is the best way to update client browser if a change occur, without refreshing the browser.
Maybe it's like facebook notification system.
You might want to take a look at implementation of Long Polling with PHP or Comet with PHP.
Long polling is a variation of the traditional polling technique and
allows emulation of an information push from a server to a client.
With long polling, the client requests information from the server in
a similar way to a normal poll. However, if the server does not have
any information available for the client, instead of sending an empty
response, the server holds the request and waits for some information
to be available. Once the information becomes available (or after a
suitable timeout), a complete response is sent to the client. The
client will normally then immediately re-request information from the
server, so that the server will almost always have an available
waiting request that it can use to deliver data in response to an
event.
Related
Good afternoon.
I have the following code, that on submit, sends data to a PHP file, which queries multiple network nodes for health status. The problem is that the tasks take about 40 seconds to complete and during that time there is no output. I tried to use ob_flush and flush. No effect, although I have in the php portion of the code. I still see the loading message and get the complete printout once it's ready. However, flush and ob_flush works in general on my server (tested as standalone script), so that's not the issue.
In my understanding that's the jQuery/ajax call that waits for the code to execute completely before spitting out the printout. I looked through the forums and couldn't find any applicable solution, as most of them are related to "GET" request while I'm using "POST".
Can someone please point me in right direction on this? Is there a way to receive printout while the PHP is still processing the request?
JS Code
$(document).ready(function(){
$('#userForm3g').on('submit', function(e){
e.preventDefault();
e.stopImmediatePropagation();
$('#response').html("<b>Loading data...</b>");
$.ajax({
type: 'POST',
url: 'myphpfile.php',
data: $(this).serialize()
})
.done(function(data){
$('#response').html(data);
})
.fail(function() {
alert( "Posting failed." );
});
return false;
});
});
Thanks!
The problem with the approach you mentioned is that there are multiple ways that it can fail: you might forget to clear the php output buffer, or the setting might be tightly controlled for some reason, there could be a proxy or load balancer that waits for the request to complete, or it could also be the web browser (chrome used to render partial content, but they stopped doing this).
There are few answers though:
You could use partial responses (which is basically streaming on http). There's a specialized library to do this which I've used before, but I forgot its name. I wouldn't recommend this option though, if it fails it will be tough to find why.
You could use any method of long polling, including comet or sockets, but you'll need a compatible server (node.js or reactphp)
You could use a 3rd party service like Pusher or OneSignal (they also use the previous approach, but it's more integrated and reliable)
As I'm currently in the process of making a forum system which is loading new posts/edits without having to refresh the page. Now, for the older browers which don't have an implentation of EventSource/WebSocket, I'd like to offer another option:
Every X seconds I'm GET'ing a PHP site which is echoing the five latest news. Afterwards, I'm simply checking which of those news weren't seen by the client yet and applying the changes to the page.
Now, my problem is: How would you determinate the X interval in which the client is retrieving new updates? I'd like to base it up the user's connections so that it isn't killing off his connection completely.
What would be your attempt at accomplishing this?
I would use long polling technique through AJAX in your case:
1) The client sends the AJAX HTTP-request to the server.
2) If there is an available data, server sends HTTP-request to client, otherwise instead of sending an empty response immediately, server holds the request and waits for information to become available (or for a suitable timeout event - for example, in every 25 seconds), after which a complete response is finally sent to the client.
3) After recieving the HTTP-respose, client immediately sends other HTTP-request to server.
I would do the following (code not tested, but you should get the idea). Use jQuery for simpler code.
function refreshNews() {
$.ajax({
url: "ajax-url"
}).done(function(data){
/** add code here */
setTimeout(function(){ refreshNews(); }, 30000); // 30 secs should be enough to read some headlines
});
}
refreshNews();
This way the refreshNews() function is only called after the data is received and shown to the user.
Just an idea: make a HTTP request and see how much it will take long and use it as the base! I'd repeat it, let say each 10 minutes to show how much I'm thinking about my clients!
I think it will be more resource-friendly on the server-side comparing to the long polling, especially for scripts like forums where people won't left the page for less than 10 hours. :)
im creating a messaging feature that gets the latest messages from a database every few seconds, basically this method does a continuous database search in order to display new messages.
example of the code:
function getLatestActivities(){
var ignoreMessagesArr = $("input.activityId").map(function(){ return this.value; }).get().join(",");
var profileId = $("input#userActivityId").val();
$.ajax({
traditional: true,
dataType: "json",
type: "GET", url: "include/process.php",
data:{
getLatestActivity: "true",
toUser: profileId,
ignoreMessages: ignoreMessagesArr
},
success: function(data){
$.each(data, function (i, elem) {
$('.commentMessage').after(elem.value);
});
}
});
}
What I want to know is whether there is a more efficient way of performing this task, i.e. detecting a change in the database instead(???).
It sounds like you want your web app to receive data when it changes in the database, but not necessarily to send data in real time. If two way communication is required then you are looking for Web Sockets which Socket.IO will help you with server side but requires that you run a Node server. There is a Google code project that enables Web Sockets for PHP called PHPWebSocket but, if I remember right, requires that you run it in a separate process (i.e. run it from the command line). So that kind of takes care of the server part, but now you have to worry about the front-end.
Currently only FireFox and Chrome fully support Web Sockets according to CanIUse. For those browsers lacking support you need a polyfill. Here is a list of HTML5 polyfills. So Web Sockets can be sort of a mess to implement, so make sure that's what you want to do.
On the other hand if your webapp only needs to receive data then EventSource (a.k.a. Server Sent Events) is the way to go. The support is better on the front-end and you don't really have to do much on the server. Again, for less than stellar browsers you will need a polyfill, but that pretty much just means IE. See the following sites/tutorials on how to use this feature.
http://my.opera.com/WebApplications/blog/show.dml/438711
http://dsheiko.com/weblog/html5-and-server-sent-events
http://www.html5rocks.com/en/tutorials/eventsource/basics/
If none of that works there are a few options. Constant polling using some kind of repeating structure like setTimeout, long polling (a.k.a. hanging get) where the server leaves the AJAX request open until there is new data, and there's also the infinite iframe trick, or maybe even a Flash plugin that connects to the server to get data.
You might want to look into Socket.IO it's geared toward realtime communications with the server. Then you can design the backend to push data to the client when it's available rather than constantly polling the database for new information from the frontend
HTML5 Web Sockets allows for two way communication between the client and your server...
In my opinion you should request only the last ID inserted in your database and add it as a parameter to to your ajax request.
process.php should handle that ID and if there are other rows to do the search.
like
$query = mysql_query("SELECT `ID` FROM `table` WHERE `ID`>'$lastId'");
$result = mysql_num_rows(); //use that to see if you have new rows.
At the moment I’ve got one function to check, if a webpage is reachable. I’ll call this function at about 100 times in a while-loop, which means it sometime lasts 5 minutes to check all these 100 webpages.
I never before used ajax but I would think that it would be a good idea to solve this problem with ajax, but I never used ajax before and have no idea, how to start. Could you give me a good hint? Thanks for every answer!
I would use jquery-ajax, makes it simpler.
So put jquery on your site to start.
This is how jquery ajax works:
$.ajax({
type: 'POST',
url: '--LINK TO PHP/ASP...---', // Place the link that has the command
data: dataString, // dataString is a json encode of the data that is sent to the file
dataType : 'json',
beforeSend:function(){
// Before you send the info, do what you want here (ie loading gif...)
},
success:function(data){
// If it is successful, then it will do what you want here.
}
});
I hope this helps.
I would suggest you use JQuery Ajax, easier to implement.
$.ajax({
url: "test.html",
context: document.body,
success: function(){
$(this).addClass("done");
}
});
From your (somewhat ill-defined) description, I'd say that using AJAX to control the web site verification would be a deeply in-appropriate approach.
Instead, a more sensible approach would be to "batch process" the web site data via the use of a cron triggered PHP cli script.
As such, once you'd inserted the relevant domains into a database table with a "processed" flag set as false, the background script would then:
Scan the database for web pages that aren't marked as checked within your required time period.
Carry out the CURL lookup, etc.
Update the database record accordingly with the current timestamp.
...
To ensure no overlap with an existing executing batch processing script, you should only invoke the php script every five minutes from cron and (within the PHP script itself) check how long the script has been running at the start of the "scan" stage and exit if its been running for four minutes or longer. (You might want to adjust these figures, but hopefully you can see where I'm going with this.)
By using this approach, you'll be able to leave the background script running indefinitely (as it's invoked via cron, it'll automatically start after reboots, etc.) and simply add web pages to the database/review the results of processing, etc. via a separate web front end.
You could of course use AJAX to get a regular summary of the current status from the database for the purposes of client-side display.
I am wondering if anyone could show, or explain with examples, how facebook checks its database for new messages? It seems to do it periodically, without loading the page. What would be the best way to achieve this in a PHP/MySQL/Jquery script?
Any help is always appreciated!
Cheers, Lea
you can do this: usign periodical updater
<span id="inbox-title"></span>
<script>
$.PeriodicalUpdater('/path/to/service', {
method: 'get', // method; get or post
minTimeout: 1000, // starting value for the timeout in milliseconds
maxTimeout: 8000, // maximum length of time between requests
}, function(data) {
$('#inbox-title').html('you have ' + data + 'new messages');
});
</script>
another option is to bind the onmousemove event and make the ajax call when than happes
There is actually a "page load", but it's a hidden request that doesn't reload the displayed page. Take a look at the jQuery Ajax command documentation for more details on one of the simplest ways to accomplish this (especially since you already mentioned using jQuery).
Have a look into reverse ajax with the COMET technique, this is a perfect use for it.
The idea behind it is to start an ajax request and let it timeout which could be 60 seconds, when it times out, start it again, here the browser has a (nearly) persistent connection to the server, if (for a simple example) a message gets created for a user. the server can reply to one of the hanging ajax requests that have been made (in this case by the recipient of the message).
No data is transfered while the xmlhttprequest and the server are waiting, but closing and reopening connections might be a burden on your server.