Run php script without cron to do automatic database backup

Question

I am trying to run a php script without cron and succeeded but doesn't work as I expected. I want the script to make a backup every 50 minutes, but it doesn't do that, it makes them continuous. This is what I tried:

cron.php

<?php
$interval=50; //minutes
set_time_limit(0);
ignore_user_abort(true);
while (true)
{
    $now=time();
    include("backup.php");
    sleep($interval*60-(time()-$now));
}
?>

backup.php

<?php
error_reporting(E_ALL);
ini_set('display_errors', 1);
$username = "user";
$password = "pass";
$hostname = "dbs";
$dbname   = "dbs_name";

// if mysqldump is on the system path you do not need to specify the full path
// simply use "mysqldump --add-drop-table ..." in this case
$dumpfname = $dbname . "_" . date("Y-m-d_H-i-s").".sql";
$command = "mysqldump --add-drop-table --host=$hostname --user=$username ";
if ($password)
$command.= "--password=". $password ." ";
$command.= $dbname;
$command.= " > " . $dumpfname;
system($command);

// zip the dump file
$zipfname = $dbname . "_" . date("Y-m-d_H-i-s").".zip";
$zip = new ZipArchive();
if($zip->open($zipfname,ZIPARCHIVE::CREATE))
{
    $zip->addFile($dumpfname,$dumpfname);
    $zip->close();
}

// read zip file and send it to standard output
if (file_exists($zipfname)) {
    header('Content-Description: File Transfer');
    header('Content-Type: application/octet-stream');
    header('Content-Disposition: attachment; filename='.basename($zipfname));
    flush();
    //readfile($zipfname);
    //exit;
}
?>

Community · Accepted Answer · 2017-05-23 10:30:55Z

First read this: PHP is meant to die.

For your Problem, You have several things to consider:

is set_time_limit(0); allowed?
your webserver could also have a seperated maximum execution time

Also sleep, is not very acurate (but for this usecase acurate enough). If you realy don't have access to cron, i would check the both steps about. If you have access to cron, i would realy consider to use it (If your on windows, take a look at scheduled tasks).

A workaround could be, on every visitor call, you check for a file lastbackup.txt and check for the last backup time. If it is older then 50 minutes/not availible, you could write the current timestamp in this file and execute the backup script after flushing output.

Sure, with this way it will not 100% executed every 50 Minutes, but if it will not, there is nothing big to backup

Max execution time Nginx:

http {
    #...
        fastcgi_read_timeout 300; 
    #...
}

Max execution time Apache:

FastCgiServer /var/www/cgi-bin/php-cgi-5.3.1 -idle-timeout 120

Max exectuion time IIS:

<system.web>
    <httpRuntime executionTimeout="180" />
</system.web>

There is also a free web based cron availbile: https://cron-job.org/ (Don't know if it also on english), but i am sure, there is more then this.

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