I have a PHP script that takes about 10 minutes to complete.
I want to give the user some feedback as to the completion percent and need some ideas on how to do so.
My idea is to call the php page with jquery and the $.post command.
Is there a way to return information from the PHP script without ending the script?
For example, from my knowledge of this now, if I return the variable, the PHP script will stop running.
My idea is to split the script into multiple PHP files and have the .post run each after a return from the previous is given.
But this still will not give an accurate assessment of time left because each script will be a different size.
Any ideas on a way to do this?
Thanks!
You can echo and flush() output, but that's suboptimal and rather fragile solution.
For long operations it might be good idea to launch script in the background and store/updte script status in shared location.
e.g. you could lanuch script using fopen('http://… call, proc_open PHP CLI process or even just openg long-running script in an <iframe>.
You could store status in the database or in shared memory (using apc_store()).
This will let user to check status of the script at any time (by refreshing page, or using AJAX) and user won't lose track of the script if browser's connection times out.
It also lets you avoid starting same long script twice.
Related
I am making an AJAX call to a PHP script that takes a long time to run. Now, assume it takes 20 minutes to run. Also assume that I either refreshed or closed then opened the web page that intiated the call. My questions are:
Does my PHP scrip stop running?
If it keeps running, how can I force a response back to the page after it was refreshed?
Thanks.
************* UPDATE *************
Some are asking why I have a script that takes a long time. I think it is my fault of not explaining the following:
a. This script is only available to site admins, and is not available to the general public
b. This script will perform some heavy lifting, such as data manipulation and database related stuff, and will require a long time to run
c. I am using AJAX so that I could still return to the main page, with a spinner showing that the script is running, while the script actually runs in the back end, and the call back function will remove the spinner and display a message of either success/failure status.
No it will stop running.
You should be using a cron job instead to run a script that will take 20 minutes.
Dont forget to set the time limit to at least 20 minutes for that page!
Does my PHP script stop running?
Yes, PHP will cease execution if the browser disconnects (which it will on refresh/close). You can use ignore_user_abort(true) to prevent this, but I don't think that would be the best option for what you want.
If it keeps running, how can I force a response back to the page after it was refreshed?
No because the connection is gone, there is nothing to send a response back to. It would be more appropriate to invoke your long process as a background process when the ajax calls it, and immediately return a response, leaving the background process to work. You can use regular ajax calls to query if the process is complete (update a database for example on completion).
From the docs:
The default behaviour is however for your script to be aborted when the remote client disconnects.
Situation:
My php/html page retrieves the contents of another page on a different domain every 5-10 minutes or so. I use a JavaScript setInterval() and a jquery .load() to request content from the other domain into an element on my page. Each time it retrieves content, javascript compares new content with the previous content and then I make an Ajax call to a php script that sends me an email of what the changes are.
Problem:
It's all working fine and dandy except for the fact that I need a browser constantly open, requesting the updates.
Question:
Is there a way to accomplish this with some sort of 'self executing' script on the server? Something that I would only have to start once, and it continues to run on it's own without needing a browser to be open as long as I want the script to run?
Thanks in advance!
P.S. I'm not a php/javascript expert by any means, but I can get my way around.
I believe the thing you are looking for is a cron job.
If your script relies on Javascript for proper execution, you will need to use a browser to accomplish your goals.
However, if you can alter your script to perform all of the functionality via PHP, perhaps using cURL to request the necessary data, you can use a cron job to execute the script at regular intervals.
If you're running a script at an interval, I would recommend using a bash script instead that runs in the background.
#!/bin/bash
while [ 1 ]
do
php "script.php"
sleep 300
done
Then you can run the script like nohup bash.sh. 300 seconds = 5 minutes.
Problem:
I'm trying to see if I can have a back and forth between a program running on the server-side and JavaScript running on the client-side. All the outputs from the program are sent to JavaScript to be displayed to the user, and all the inputs from the user are sent from JavaScript to the program.
Having JavaScript receive the output and send the input is easily done with AJAX. The problem is that I do not know how to access an already running program on the server.
Attempt:
I tried to use PHP, but ran into some hurdles I couldn't leap over. Now, I can execute a program with PHP without any issue using proc_open. I can hook into the stdin and stdout streams, and I can get output from the program and send it input as well. But I can do this only once.
If the same PHP script is executed(?) again, I end up running the program again. So all I ever get out of multiple executions is whatever the program writes to stdout first, multiple times.
Right now, I use proc_open in the script which is supposed to only take care of input and output because I do not know how to access the stdout and stdin streams of an already running program. The way I see it, I need to maintain the state of my program in execution over multiple executions of the same PHP script; maintain the resource returned by proc_open and the pipes hooked into the stdin and stdout streams.
$_SESSION does NOT work. I cannot use it to maintain resources.
Is there a way to have such a back and forth with a program? Any help is really appreciated.
This sounds like a job for websockets
Try something like http://socketo.me/ or http://code.google.com/p/phpwebsocket/
I've always used Node for this type of thing, but from the above two links and a few others, it looks like there's options for PHP as well.
There may be a more efficient way to do it, but you could get the program to write it's output to a text file, and read the contents of that text file in with php. That way you'd have access to the full stream of data from the running program. There are issues with managing the size of the file, and handling requests from multiple clients, but it's a simple approach that might be good enough for your needs.
You are running the same program again, because it's the way PHP works. In your case client does a HTTP request and runs the script. Second request will run the script again. I'm not sure if continuous interaction is possible, so I would suggest making your script able to handle discrete transactions.
In order to figure different steps of the same "interaction", you will have to save data about previous ones in database. Basically, you need to give some unique hash to every client to identify them in your script, then it will know who does the request and will be able to differ consecutive requests from one user from requests of different users.
If your script is heavy and runs for a long time, consider making two script - one heavy and one for interaction (AJAX will query second one). In this case, second script will fill data into database and heavy script will simply fetch it from there.
I am working in a tool in PHP that processes a lot of data and takes a while to finish. I would like to keep the user updated with what is going on and the current task processed.
What is in your opinion the best way to do it? I've got some ideas but can't decide for the most effective one:
The old way: execute a small part of the script and display a page to the user with a Meta Redirect or a JavaScript timer to send a request to continue the script (like /script.php?step=2).
Sending AJAX requests constantly to read a server file that PHP keeps updating through fwrite().
Same as above but PHP updates a field in the database instead of saving a file.
Does any of those sound good? Any ideas?
Thanks!
Rather than writing to a static file you fetch with AJAX or to an extra database field, why not have another PHP script that simply returns a completion percentage for the specified task. Your page can then update the progress via a very lightweight AJAX request to said PHP script.
As for implementing this "progress" script, I could offer more advice if I had more insight as to what you mean by "processes a lot of data". If you are writing to a file, your "progress" script could simply check the file size and return the percentage complete. For more complex tasks, you might assign benchmarks to particular processes and return an estimated percentage complete based on which process has completed last or is currently running.
UPDATE
This is one suggested method to "check the progress" of an active script which is simply waiting for a response from a request. I have a data mining application that I use a similar method for.
In your script that makes the request you're waiting for (the script you want to check the progress of), you can store (either in a file or a database, I use a database as I have hundreds of processes running at any time which all need to track their progress, and I have another script that allows me to monitor progress of these processes) a progress variable for the process. When the process begins, set this to 1. You can easily select an arbitrary number of 'checkpoints' the script will pass and calculate the percentage given the current checkpoint. For a large request, however, you might be more interested in knowing the approximate percent the request has completed. One possible solution would be to know the size of the returned content and set your status variable according to the percentage received at any moment. I.e. if you receive the request data in a loop, each iteration you could update the status. Or if you are downloading to a flat file you could poll the size of the file. This could be done less accurately with time (rather than file size) if you know the approximate time the request should take to complete and simply compare against the script's current execution time. Obviously neither of these are perfect solutions, but I hope they'll give you some insight into your options.
I suggest using the AJAX method, but not using a file or a database. You could probably use session values or something like that, that way you don't have to create a connection or open a file to do anything.
In the past, I've just written messages out to the page and used flush() to flush the output buffer. Very simple, but it may not work correctly on every web server or with every web browser (as they may do their own internal buffering).
Personally, I like your second option the best. Should be reliable and fairly simple to implement.
I like option 2 - using AJAX to read a status file that PHP writes to periodically. This opens up a lot of different presentation options. If you write a JSON object to the file, you can easily parse it and display things like a progress bar, status messages, etc...
A 'dirty' but quick-and-easy approach is to just echo out the status as the script runs along. So long as you don't have output buffering on, the browser will render the HTML as it receives it from the server (I know WordPress uses this technique for it's auto-upgrade).
But yes, a 'better' approach would be AJAX, though I wouldn't say there's anything wrong with 'breaking it up' use redirects.
Why not incorporate 1 & 2, where AJAX sends a request to script.php?step=1, checks response, writes to the browser, then goes back for more at script.php?step=2 and so on?
if you can do away with IE then use server sent events. its the ideal solution.
Basically I need to get around max execution time.
I need to scrape pages for info at varying intervals, which means calling the bot at those intervals, to load a link form the database and scrap the page the link points to.
The problem is, loading the bot. If I load it with javascript (like an Ajax call) the browser will throw up an error saying that the page is taking too long to respond yadda yadda yadda, plus I will have to keep the page open.
If I do it from within PHP I could probably extend the execution time to however long is needed but then if it does throw an error I don't have the access to kill the process, and nothing is displayed in the browser until the PHP execute is completed right?
I was wondering if anyone had any tricks to get around this? The scraper executing by itself at various intervals without me needing to watch it the whole time.
Cheers :)
Use set_time_limit() as such:
set_time_limit(0);
// Do Time Consuming Operations Here
"nothing is displayed in the browser until the PHP execute is completed"
You can use flush() to work around this:
flush()
(PHP 4, PHP 5)
Flushes the output buffers of PHP and whatever backend PHP is using (CGI, a web server, etc). This effectively tries to push all the output so far to the user's browser.
take a look at how Sphider (PHP Search Engine) does this.
Basically you will just process some part of the sites you need, do your thing, and go on to the next request if there's a continue=true parameter set.
run via CRON and split spider into chunks, so it will only do few chunks at once. call from CRON with different parameteres to process only few chunks.