On Mon, 2010-03-15 at 18:07 +1030, David Robley wrote:

> Alex Major wrote:
> > Greetings all,
> > 
> > I'm currently looking at building a web application, however I've run into
> > an area of development I've not come across before. The web site in its
> > basic form allows users to send cars from a point and then the car will
> > arrive at another point. When the car is set on its way, the start time,
> > travel duration and end time are all known and stored in a MySQL database,
> > what I would like to happen is that an event is triggered on the server at
> > the end time and then an e-mail is sent to the user. This should happen
> > regardless of whether someone is browsing the website or not.
> > 
> > I don't believe that I'll be able to solely use PHP, I have spent the
> > afternoon trying to look at potential solutions but I have to admit I've
> > drawn a blank. Google hasn't been helpful (64 pages so far), as any
> > searches related to "event handling" bring up a load of JavaScript
> > tutorials/help for 'onclick' events etc. I have searched through the PHP
> > documentation and found "libevent"
> > (http://www.php.net/manual/en/book.libevent.php ), I don't believe that is
> > what I require (although in all honesty the lack of documentation on it
> > means I'm quite in the dark as to its purpose). Another potential
> > candidate I came across was a PHP/Java bridge
> > (http://php-java-bridge.sourceforge.net/pjb/ ), whereby I could use the
> > java virtual machine, register events with it and then callback PHP
> > scripts, although this seems extremely long winded.
> > 
> > I was hoping that someone might have some experience with this kind of
> > issue and could point me in the right direction. I'm sure I've missed
> > something right in front of me.
> > 
> > Alex.
> I think what you want is something to trigger a php script every
> $period-of-time; if your host supports it, cron is the means of executing
> an application at regular intervals down to a minute granularity. There are
> some web-based cron services also, but they may not have the same
> granularity as a locally based cron.
> Cheers
> -- 
> David Robley
> "Wow!" barked Tom, with a bow.
> Today is Prickle-Prickle, the 1st day of Discord in the YOLD 3176. 

You could store the end times in the database, and cron can run a script
that will check each of these times to find any that are within x
minutes that an email hasn't been sent out for. You'll need an extra
field to indicate whether an email has been sent or not.


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