[RESOLVED] Can PHP do stuff in the background??

mark_79_smith

Hi,

Here's my situation. I'm creating a website (basically a store) and in the admin section users will want to download zip files of images or products added in the last 7 days, last 2 weeks and the last month.

I have scripted a cron to run every 24 hours to zip all the images and this process takes over 1 minute (there's over 6,000 images!!) and the size of this is 250MB. This has now taken me to my quota on my webspace of 500MB (including all the individual images)

I have decided the only way to do this is dynamically create the zip when the user requests it. As PHP times out after 30 seconds it needs to do it's stuff in the background and display a message saying something like' We'll email you with the zip file in 5 minutes or so'.

Is this possible?

subwayman

Yes but you may run up against the same problem as the zip files will still need to occupy space as it is created and as it is attached to the email. Again you would use cron but have the script running every minute or so picking up and serving requests for the file(s).

One thing you might try is to zip the files up without compression. This may sound odd but most images are compressed anyway and zipping them with compression saves very little extra space. Zipping without compression is very much faster and you may find it can be done within the timeout. Of course you could set the timeout to a longer time (look at php.ini and/or your server config).

justsomeone

I strongly suggest that you're tackling this the wrong way. If you have a single file using 50% of your diskspace, you need to get more diskspace. Do whatever it takes to get more quota. Otherwise you're going to have to resort to "clever hacks" which could get you into trouble, unless you make them utterly robust.

For instance, if User A requests the file download, and User B requests it a couple of seconds later - will that create two zips, using double the space? Or will B "inherit" A's zip? if that's the case, what happens if A deletes if before B downloads it? Or if A aborts/crashes and only creates a partial file?...

You very quickly build up a fairly messy set of conditions to deal with. Without any great reason for it. Once anyone requests the file, your space is used anyway.

Also, how many times will you be able to email a 250MB file before your host cracks down on your bandwidth usage?

Get the extra quota. You need it.

If you really can't get the quota, you could try a different approach. Do you need to send down the images at all? Could you just send down a link to the images instead, and let your adminnners download the individual images they require. Do they really want a 250MB attachment on their email?

Weedpacket

Agreements with the observations of the others. Another observation is that since email is a pure-text format, binary data has to be encoded as text before it can be attached; in the process it ends up 25% larger - 250MB becomes more than 300MB. So not only are you using 250MB to store the images, plus 250MB to construct the zip file, but you also need 300MB+ to construct the email. Streaming could alleviate some of that, but it's still a massive job no matter how you look at it.

mark_79_smith

Hi Guys,

Thanks very much for your input. I have changed my host which allow me a massive 3GB of space for an extra £5 per month. I also have decided against sending the zip file by email, but by providing a download link after the zip has been created.

Thanks very much.