Continue to process after page has been displayed

cmay4

I am trying to do something that I think should be pretty staightforward, but I can't seem to figure it out. I have a page which prompts the user for a set of criteria. The thing is that the process that takes place after submit is pressed can take a very long time. I'd like to just show the user a page after submitted that says that they will receive an e-mail when it it completed. That way they don't have to wait, and can use the rest of the site in the meantime.

So, I am trying to display a quick message and then start processing. The problem is that I can't get the page to "finish" until the long process is actually completed. I output the closing HTML tag, and call flush() before starting the long process. The screen is updated and looks like it's done. However I can't access other links on the site until the main process is completed.

I am wondering what exactly happens with you call "exit()". It tells Apache, which tells the browser, that everything is completed. There must be some way to emulate that without actually exiting the PHP script.

I tried the register_shutdown_function, but it doesn't seem to get called until the script exits.

I thought about the command-line PHP, which I don't currently have installed, and launching it as a background process. Is that my only option?

Chuck

viper21634

Rather than just working around the problem, I would suggest that you start at the beging of the code and and after every major code segment add in the die; command and see what happenes, if your script stops then you know the problem is further down, so take the die and move it lower, when you find the point at which it "locks up"(that will be when it does what it has been doing before) you can look VERY carefully at the code and you will probally see something that is not correct. If not PM me the code and let me look at it.

cmay4

There is no "locking up" problem...

I want to display a page and then run thought some very time consuming code that I don't waht the browser to wait for. For example:

// output page
echo "You will be e-mailed upon completion...";

echo "</html>";
flush();

// at this point, I'd like the browser to be completely finished
// with this request, but I'd like the php script to start processing
// some queries

for ($i = 0; $i < 1000000; $i++) {
   // do something here...
}

// send e-mail to user that the request is complete

No matter what I do, the client isn't finished displaying the page until the script exits, or I explicitely call exit();

I'd like to find a way to emulate what exit dies, without actually leaving the script.

Does that make sense?

Chuck

viper21634

ohhh, ok i see what you are saying

ok, what you want to do is something like this

<html>
<body>
<?php
echo "You will be e-mailed upon completion...";
flush();
?>
</body>
</html>
<?php
for ($i = 0; $i < 1000000; $i++) {
   // do something here...
}

// send e-mail to user that the request is complete
?>

that way the browser gets everything that is going to it, and your script can run

cmay4

I'm not sure that will work. I using templates, and not imbedded php within an html file. Are you saying that at the end of each <?php block, all the handles are closed?

Here is the basic code:

<?php
$root_path = './';
include($root_path . 'common.php');

session_pagestart("dump.php");  // handle session management and login

include_once($root_path . 'includes/db.php');  // make database connection

// Start output of page
$page_title = $lang['Data_dump'];
include($root_path . 'includes/page_header.php');

if (isset($HTTP_POST_VARS['studyid']) || isset($HTTP_GET_VARS['studyid'])) {
    $study_id = isset($HTTP_POST_VARS['studyid']) ? $HTTP_POST_VARS['studyid'] 
                       : $HTTP_GET_VARS['studyid'];

$template->set_file('t_dump_result', 'data_dump_result_body.tpl');
$template->set_var(array(
   'DUMP_SUBMITTED' => sprintf($lang['Dump_submitted'], $study_id, $_SESSION['email'])
));
$template->pparse('t_output', 't_dump_result');

include($root_path . 'includes/page_tail.php');

// make the database connection
include_once('adodb/toexport.inc.php');

$sql = "SELECT v.*, s.subject_id, s.date_drawn, s.date_last_modified
        FROM   vial v, sample s 
        WHERE  v.sample_id = s.sample_id 
        AND    study_id = '$study_id'";

$rs = $con->Execute($sql);

// get the temporary filename
$csv_file = get_temp_name($_SESSION['user_name'], $_SESSION['database']);
$csv_file .= '.csv';

$fp = fopen($csv_file, "w");   // open the output file
rs2csvfile($rs, $fp);
fclose($fp);   // close the file

// e-mail notification to user
preg_match('/(.*)\.(.*)\.(.*).csv$/', $csv_file, $match);
list(,,,$base_name) = $match;

$message = 'Report is available at [url]https://[/url]' 
       . $HTTP_SERVER_VARS["HTTP_HOST"] 
       . '/download.php/?do=' 
       . $_SESSION['user_name']  . '.' . $base_name;

send_mail($_SESSION['email'], 'Data Dump', $message);
}
else {
    // display page where user make choice

$form_action = append_sid('data_dump.php');
$template->set_file('t_dump', 'data_dump_body.tpl');

$template->set_var(array(
  'INSTRUCTIONS' => $lang['Dump_instructions'],
  'L_STUDY_ID'   => $lang['Study_ID'],
  'L_RUN_DUMP'   => $lang['Run_dump'],
  'DUMP_TITLE'   => $lang['Data_dump'],
  'FORM_ACTION'  => $form_action
));;

// Generate the page
$template->pparse( 't_output', 't_dump' );

include($root_path . 'includes/page_tail.php');
}

?>

cmay4

I rearranged the file so that it had multiple <?php> blocks, and it still didn't release control of the page. I think I just need to find out exactly what exit is doing to trigger apache to signal the end of a page.

Chuck

devinemke

exit() does exactly what is says, it stops the script. If you call exit() the parser will stop at that line and not complete the rest of your script. This is not what you want. I don't really know that there is a way to continue a script execution after output to the browser.

cmay4

I assume the last resort is to do the long operation in a seperate script that is launched as a background process

exec('script.php &');

I figure that would work. However, I don't have the CLI php installed.

Chuck

cmay4

Ok...I'm trying to launch a script which will continue to run after the apache process ends. I am using:

exec('./send_some_mail > /dev/null &');

The problem is that once the php script ends, the send_some_mail process dies. If the script is really quick, it works fine. If it takes a little bit of time, then it dies before it gets to complete it's task. Does anyone have any ideas?

Chuck

azkworld

We had a similar issue, and the solution we use very successfully is to post a flag to db (or, rather, add a row to db table "process_queue"), and have a cron job run every minute on a script process_queue.php which simply selects all outstanding tasks from db and runs them. We don't need it to be any more often, but we have tested it for every 5 seconds while adding 1000 new rows per minute to queue.

Weedpacket

Does anyone use register_shutdown_function for this sort of thing (get the data, register the slow business in a function, send the response, end of script)? Does that still tie up the client?

cmay4

I tried the register_shutdown_function. The one problem I ran into was that inside the shutdown function, the current working directory is reset, so I had to track it through getcwd(). Not a big deal.

However, as the shutdown function is running, the page is completely displayed, the "globe" in the corner of IE is still spinning, like it's still loading. In addition, I can't link away from the page until the process is completed.

The documentation for register_shutdown_function indicates that the page should be completely loaded and the connection closed when it's inside of the specified shutdown function. This does not seem to be the case.

Chuck

herve

Hi,

may be with system() or shell_exec() instead
of exec() call ?

see:

http://www.php.net/manual/en/ref.exec.php

for more info

Hervé.

azkworld

http://www.php.net/manual/en/function.register-shutdown-function.php
addresses your issue and more.