Getting PHP processing to happen in the background - php

Question

I am working on a PHP website, and I am moving it over to a new server. The new server I am moving to does not have CRON compatibility. To compensate for this I have devised a system using time formats and database tables and more to run my code instead.
What I am having a problem with is this bit of code:
if ($lasttime < $pretime)
{
$newtime = strtotime("now");
queryMysql("UPDATE time SET time=".$newtime." WHERE time=".$lasttime);
include_once 'grabber/grabber.php';
}
Specifically it's the include_once 'grabber/grabber.php'; which is causing the problem. When the timer comes round and this code runs, it gets to the include and then the code stops, with no error provided, so the include fails. I have tried changing it to an exec() but to be honest I don't completely understand how exec() works and if it is the correct thing to do. This is how I used it:
if ($lasttime < $pretime)
{
$newtime = strtotime("now");
queryMysql("UPDATE time SET time=".$newtime." WHERE time=".$lasttime);
$grabber = $base."grabber/grabber.php";
exec($grabber);
}
This does not stop the code and seems to run but it doesn't actually work, if grabber/grabber.php runs correctly then I get an email to confirm using the PHP mail() function
If anyone could help me solve this or shed some light that would be brilliant.
Thanks.

Answer 1

This is most probably an issue with the file location or permissions. There should be some kind of error, or the code doesn't stop, but you don't properly check that or there is some kind of an issue with the code in grabber.php itself. Add some debugging lines - print the filename, so you can check for errors in the path/name; add error_reporting(E_ALL); ini_set('display_errors', true); somewhere above the include_once line; make sure the file is where you're trying to open it from, taking into account relative paths, etc. Make sure you have permissions to run this file.
exec() is not what you need in this case, at least not in the way that you're trying to use it.
If that doesn't help - give some more information about how you run the scripts that you've shown, what's in the grabber.php file, what errors you get, etc.

Answer 2

(Assuming your server is *nix) If you want to use exec() you need to place a hashbang at the top of the script that points to the PHP executable and give it execute permissions.
Or (this is probably the better/more portable approach), change
$grabber = $base."grabber/grabber.php";
exec($grabber);
to
$grabber = "php ".$base."grabber/grabber.php";
exec($grabber);
...as if you were running it from a terminal.
However, I doubt this will solve the problem - I think the answer is more likely to be one of these things:
A parse error in grabber.php. Keep in mind that there are slight syntax differences between major PHP versions - if your PHP version is different on your old/new hosts, this may be the problem.
A call to a function that was defined on your old host but not on your new host, because of a difference in PHP version or installed extensions
grabber.php was corrupted during the move between servers
Try it with the include_once, but do ini_set('display_errors',1); error_reporting(-1); to make sure you actually see any errors. How are you calling you main script? How will you see the errors? Edit the question with this info, any code from grabber.php you think may be relevant and I will expand this answer.