I want to update a page when my database is modified. I want to use jquery for doing this. Question not clear? Then have a look at this, Suppose this is my page:
<?php
$query=mysql_query("select * from tbl1 where user='admin'");
if(mysql_num_rows?($query)!=0)
{
echo 'Table 1 has values';
} else {
echo 'Table1 is empty';
}
?>
This action should be performed whenever any new entry is added to the database. Now suppose I add an entry to the database manually then the page should automatically show the result as "Table1 has values". I know it can be used by using refresh page periodically but I don't want to use it. Instead I want to try something other, like ajax polling? Can someone give me a demo?
You can use long polling, but do a lot of research first. Your server may kill the request that appears to be open for a long amount of time.
In PHP, your code will look something like...
set_time_limit(0);
while (TRUE) {
// Query database here
if ($results) {
echo json_encode($results);
exit;
}
sleep(1);
}
You can use Ajax jQuery Framework with Ajax:
http://www.w3schools.com/Ajax/default.asp
http://api.jquery.com/jQuery.ajax/
It will call the server side script Asynchronously and update your page accordingly. You can use jQuery to specify the format of the update also.
You are looking for Ajax-Push/Comet solutions. These aren't trivial.
You also mentioned ajax pooling.
Well, on the server side you need to loop until you have a timeout (that you defined yourself or the server did, make sure you return the HTTP status code for Timeout Occured) or the request can be satisfied.
And on the client side whenever you complete the operation successfully just handle it and than make the same ajax call again, if you timed out just make the same ajax request again until it's satisfied.
Related
My function have for loop and once loop it's output percent of that loop. It's look like this:
function checkisset($v){
foreach ($variable as $key=>$value)
if($v==$value) echo $key/count($variable);
}
and in client i want to show process of loop.
Ex: count($varibale)=10; First time in loop it will be 10%; and when 100% will run success function.
How can i do it??
Tks everyone.
To update your webpage dynamically, you have to establish communication between the client and the server, and send updates.
One way to send updates is "Server sent events". Another is "forever frame", where the page opens javascript link to the server and the server sends javascript statements over time.
In either case, you loop with updates will be a separate resource from the main page that you intend to update.
I have a JavaScript functions which calls a PHP function through AJAX.
The PHP function has a set_time_limit(0) for its purposes.
Is there any way to stop that function when I want, for example with an HTML button event?
I want to explain better the situation:
I have a php file which uses a stream_copy_to_stream($src, $dest) php function to retrieve a stream in my local network. The function has to work until I want: I can stop it at the end of the stream or when I want. So I can use a button to start and a button to stop. The problem is the new instance created by the ajax call, in fact I can't work on it because it is not the function that is recording but it is another instance. I tried MireSVK's suggest but it doesn't worked!
Depending on the function. If it is a while loop checking for certain condition every time, then you could add a condition that is modifiable from outside the script (e.g. make it check for a file, and create / delete that file as required)
It looks like a bad idea, however. Why you want to do it?
var running = true;
function doSomething(){
//do something........
}
setInterval(function(){if(running){doSomething()}},2000); ///this runs do something every 2 seconds
on button click simply set running = false;
Your code looks like:
set_time_limit(0);
while(true==true){//infinite loop
doSomething(); //your code
}
Let's upgrade it
set_time_limit(0);
session_start();
$_SESSION['do_a_loop'] = true;
function should_i_stop_loop(){
#session_start();
if( $_SESSION['do_a_loop'] == false ) {
//let's stop a loop
exit();
}
session_write_close();
}
while(true==true){
doSomething();
should_i_stop_loop(); //your new function
}
Create new file stopit.php
session_start();
$_SESSION['do_a_loop'] = false;
All you have to do now is create a request on stopit.php file (with ajax or something)
Edit code according to your needs, this is point. One of many solutions.
Sorry for my English
Sadly this isn't possible (sort of).
Each time you make an AJAX call to a PHP script the script spawns a new instance of itself. Thus anything you send to it will be sent to a new operation, not the operation you had previously started.
There are a number of workarounds.
Use readystate 3 in AJAX to create a non closing connection to the PHP script, however that isn't supported cross browser and probably won't work in IE (not sure about IE 10).
Look into socket programming in PHP, which allows you to create a script with one instance that you can connect to multiple times.
Have PHP check a third party. I.E have one script running in a loop checking a file or a database, then connect to another script to modify that file or database. The original script can be remotely controlled by what you write to the file/database.
Try another programming language (this is a silly option, but I'm a fan of node). Node.js does this sort of thing very very easily.
I have something like this :
<?php
$perform_check = 1; #Checks data with ID : 1
while(true)
{
#code
}
?>
But some data must be updated in this process, is it possible to update this data from another document?
I tried something like this :
index.php
<?php
setcookie("data", 19, time()+3600);
?>
and
loop.php
<?php
while(true)
{
if($perform_check!=$_COOKIE[data]) $perform_check = $_COOKIE[data];
#rest of code
flush();
sleep(0.3);
}
?>
But it doesn't work. I also tried $_SESSION but the page crashes on session_start().
Is it somehow possible?
Cookies are sent as a HTTP header when PHP is sending a response through the web server (for example Apache2).
All HTTP headers are sent before any output. If you output anything, headers are sent (including the set-cookie header) before the output.
After you flush() the first time you can no longer set cookies or other headers.
If you want a progress indicator or updates, you need to initiate whatever operation you are doing using javascript and do polling at an interval. In the process with the loop you need to save the progress in a shared memory, in a file or in a database (in this order of preference), then read that data using the process started by javascript progress check/updates check.
You could use the existence of a file to flag the ending of the process. For example, create a lock file,
$lock_file = <some unique name>
fopen($lock_file, 'w') or die("can't open file");
while ( file_exists($lock_file)) {
.
.
doStuff();
.
.
}
If the file is removed by some other process, it should terminate.
I think a while loop isn't doing any good here. you should look into php websocket implementation. It's an implementation in PHP to have websockets and to have a open connection with your user. If you have that you can manage things with listeners on both sides.
If you want the value to change while your code is looping, you need to check if the value has changed within the loop, not before.
A cookie or session will only work if the same user/browser is running both scripts. Writing to a file or database is the more usual approach.
I'm not quite sure about what you really want to do here.. but i guess you could do this..
<?php
$perform_check = 1; #Checks data with ID : 1
while(true) : ?>
$.ajax({
type:'post',
data: //your data to be passed to ajax script..
url: //the script wherein you want to run the query..
onSuccess: function(data) {
if(data==test) {
//if you have data that you want then you could stop the loop
<?php $perform_check = false; ?>
}
}
});
<?php endwhile: ?>
Hope this helps.
If you need to check very often you should use a CRON that calls the function you use to check.
I have a PHP script (let's call it execute.php) that draws the whole page (HTML tags and body tags etc.) at the beginning and, afer that, executes some commands (C++ programs) in the background. It then waits for these programs to terminate (some depend on the results of others, so they may be executed sequentially) and then has a JavaScript that auto-submits a form to another PHP script (which we will call results.php) because results.php needs the POST-information from the previous script.
execute.php:
<?php
print"
<html>
<body>
Some HTML code here
</body>
</html>
";
// Here come some C++-program calls
$pid_program1 = run_in_background($program1)
$pid_program2 = run_in_background($program2)
while (is_running($pid_program1) or is_running($pid_program2) )
{
//echo(".");
sleep(1);
}
// Here come some later C++-program calls that execute quickly
$pid_program3 = run_in_background($program3)
$pid_program4 = run_in_background($program4)
while (is_running($pid_program3) or is_running($pid_program4) )
{
sleep(1);
}
...
// We are now finished
print "
<form action=\"results.php\" id=\"go_to_results\" method=\"POST\">
<input type='hidden' name=\"session_id\" value=\"XYZ\">
</form>
<script type=\"text/javascript\">
AutoSubmitForm( 'go_to_results' );
</script>
";
This works nicely if the C++ programs 1 and 2 execute quickly. However, when they take their time (around 25 minutes in total), the PHP script seems to fail to continue. Interestingly the C++ programs 3 and 4 are nevertheless executed and produce the expected outputs etc.
However, when I put a echo("."); in the first while-loop before the sleep(), it works and continues until the JavaScript autosubmit.
So it seems to me that the remaining PHP code (including the autosubmit) is, for whatever reason, not send when there is no output in the first while loop.
I have also tried using set_time_limit(0) and ignore_user_abort(true) and different other things like writing to an outputbuffer (don't want to clutter the already finally displayed webpage) instead of the echo, but none of these work.
When I run the same scripts on a machine with multiple cores, so that program1 and 2 can be executed in parallel, it also works, without the echo(".").
So I am currently very confused and can't find any error messages in the apache log or PHP log and thus would really appreciate your thoughts on this one.
EDIT
Thanks again for your suggestions so far.
I have now adopted a solution involving (really simple) AJAX and it's definitely nicer this way.
However, if the C++-programs executions take "longer" it is not autosubmitting to the results-page, which is actually created this time (failed to do so before).
Basically what I have done is:
process.php:
<?php
$params = "someparam=1";
?>
<html>
<body>
<script type="text/javascript">
function run_analyses(params){
// Use AJAX to execute the programs independenantly in the background
// Allows for the user to close the process-page and come back at a later point to the results-link, w/o need to wait.
if (window.XMLHttpRequest)
{
http_request = new XMLHttpRequest();
}
else
{
//Fallback for IE5 and IE6, as these don't support the above writing/code
http_request = new ActiveXObject("Microsoft.XMLHTTP");
}
//Is http_request still false
if (!http_request)
{
alert('Ende :( Kann keine XMLHTTP-Instanz erzeugen');
}
http_request.onreadystatechange=function(){
if (http_request.readyState==4 && http_request.status==200){
// Maybe used to display the progress of the execution
//document.getElementById("output").innerHTML=http_request.responseText;
// Call of programs is finished -> Go to the results-page
document.getElementById( "go_to_results" ).submit();
}
};
http_request.open("POST","execute.php",true);
//Send the proper header information along with the request
http_request.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
http_request.setRequestHeader("Content-length", params.length);
http_request.setRequestHeader("Connection", "close");
http_request.send(params);
};
</script>
<?php
// Do some HTML-markup
...
// Start the programs!
print "
<script type=\"text/javascript\">
run_analyses('".$params."');
</script>
<form action=\"results.html" id=\"go_to_results\" method=\"POST\">
<input type='hidden' name=\"session_id\" value=\"XYZ\">
</form>
?>
</html>
</body>
and execute.php contains the C++-program calls, waiting-routines and finally, via "include("results.php")" the creation of the results-page.
Again, for "not so long" program executions, the autosubmission works as expected, but not if it takes "longer". By "longer" I mean around 25 minutes.
I have absolutely no idea what could cause this as again, there are no error-messages to be found.
Am I missing a crucial configuration option there (apache, php, etc.)?
EDIT
As it turned out, letting the requested PHP-script "echo" something repeatedly prevents the timeout. So it is basically the same as for the PHP-solution without AJAX, but this time, since the responseText of the AJAX-request is not necessarily needed, the progress-page is not cluttered and it may be used as a workaround. Specifically, I would not necessarily recommend it a as a general solution or good-practice.
It occurs to me that a better approach would be to:
Output the complete HTML page
Show a loading message to the user
Send an AJAX request to start the external program
Wait for callback (waiting for external program to finish)
Repeat steps 3 and 4 until all program have been executed
Update the page to tell the user what is going on
Submit the form
This way, you get the HTML to the user as quickly as possible, then you execute the programs sequentially in an orderly and controlled fashion without worrying about hitting the max_execution_time threshold. This also enables you to keep your user informed - after each AJAX callback, you can tell the user that "program ABC has completed, starting DEF..." and so on.
EDIT
Per request, I'll add an outline of how this could be implemented. A caveat, too: If you are going to be adding more javascript-derived functionality to your page, you'll want to consider using a library like jQuery or mootools (my personal favorite). This is a decision you should make right away - if you aren't going to be doing a lot of javascript except this, then a library will only bloat your project, but if you are going to be adding a lot of javascript, you don't want to have to come back later and re-write your code because you add a library 3/4 of the way through the project.
I've used mootools to create this demonstration, but it isn't necessary or even advisable to add mootools if this is the only thing you're going to use it for. It is simply easier for me to write an example really quick without having to stop and think :)
First, the main page. We'll call this page view.php. This should contain your initial HTML as well as the javascript that will fire off the AJAX requests. Basically, this entire jsFiddle would be view.php: http://jsfiddle.net/WPnEy/1/
Now, execute.php looks like this:
$program_name = isset($_POST['program_name']) ? $_POST['program_name'] : false;
switch ($program_name) {
case 'program1':
$program_path = '/path/to/executable/';
$friendly_name = 'Some program 1';
break;
case 'program2':
$program_path = '/path/to/executable/';
$friendly_name = 'Some program 2';
break;
case 'program3':
$program_path = '/path/to/executable/';
$friendly_name = 'Some program 3';
break;
case 'program4':
$program_path = '/path/to/executable/';
$friendly_name = 'Some program 4';
break;
default:
die(json_encode(array(
'program_name'=>'Invalid',
'status'=>'FAILED',
'error'->true,
'error_msg'=>'Invalid program'
)));
break;
}
$pid = run_in_background($program_path)
while (is_running(pid)) {
sleep(1);
}
// check here for errors, get any error messages you might have
$error = false;
$error_msg = '';
// use this for failures that are not necessarily errors...
$status = 'OK';
die(json_encode(array(
'program_name'=>$friendly_name,
'status'=>$status,
'error'->$error,
'error_msg'=>$error_msg
)));
execute.php would then be called once for each program. The $friendly_program variable gives you a way to send back something for the user to see. The switch statement there makes sure that the script isn't being asked to execute anything you aren't expecting. The program is executed, and when it is done you send along a little package of information with the status, the friendly name, any errors, etc. This comes into the javascript on view.php, which then decides if there are more programs to run. If so, it will call execute.php again... if not, it will submit the form.
This seems rather convoluted... And very risky. Any network glitches, the user's browser closing for whatever reason, and even a firewall timing out, and this script is aborted.
Why not run the whole thing in the background?
<?php
session_start();
$_SESSION['background_run_is_done'] = false;
session_write_close(); // release session file lock
set_time_limit(0);
ignore_user_abort(true); // allow job to keep running even if client disconnects.
.... your external stuff here ...
if ($successfully_completed) {
session_start(); // re-open session file to update value
$_SESSION['background_run_is_done'] = TRUE;
}
... use curl to submit job completion post here ...
?>
This disconnects the state of the user's browser from the processing of the jobs. You then just have your client-side code ping the server occasionally to monitor the job's progress.
Launching and managing multiple and long-running processes from a webserver PHP process is fraught with complications and complexity. It's also very different on different platforms (you didn't say which you are using).
Handling the invocation of these processes synchronously from the execution of your PHP is not the way to address this. You really need to run the programs in a seperate session group - and use (e.g.) Ajax or Comet to poll the status of them.
If I'm generating a stream of data to send out to a browser, and the user closes the browser, can I tell within PHP that I don't need to bother generating or sending the rest of the stream? I'd like to insert something into this loop:
while (!feof($pipes[1])) {
echo fgets($pipes[1]);
}
My fallback plan is to have the browser use a JavaScript onunload to hit another PHP page to kill the process that's generating the data, but it would be cleaner if PHP could tell when I'm echoing to nowhere.
By default PHP will abort the script if the user navigates away. There are however times where you don't want this to happen so php has a config you set called ignore_user_abort.
http://php.net/manual/en/misc.configuration.php
There's also a function called register_shutdown_function() that is supposedly executed when execution halts. I've never actually used it, so I won't vouch for how well it works, but I thought I'd mention it for completeness.
I believe that script will automatically abort when loaded normally (No ajax). But if you want to implement some sort of long polling via php using xmlhttprequest I think you will have to do it with some sort of javascript because then php can't detect it. Also like to know the precise case.
These answers pointed me towards what I was looking for. The underlying process needed special attention to kill it. I needed to jump out of the loop. Thanks again, Stack Overflow.
while (!feof($pipes[1]) && !connection_aborted())
{
echo fgets($pipes[1]);
}
if (connection_aborted())
{
exec('kill -4 '.$mypid);
}