Screen size check withOUT using forms?

[bbirney]

Here's an interesting challenge I've been scratching my head over for the last few days. I need to figure out some way to do a server-side check on the visitor's screen size without using ASP. And I need to do it while preserving the functionality of the back button.

Unfortunately, this rules out the ingenious Javascript/forms/PHP trick that's floating around out there - an excellent bit of logical tomfoolery, that, but it does act as a redirect, thus messing up the back button.

The basic problem here seems to be that the header transmitted to the server when a client accesses a page does not include the client's screen size. Perl, PHP and even ASP don't have that as one of their environment variables, though I've heard that ASP gets around it by embedding JavaScript, which has access to the DOM. (Haven't tried this myself, as the server I'm working with doesn't run any form of ASP.)

So... anybody have any bright ideas on how to do this? I'm not that hopeful, since the most popular approach out there, the JavaScript/form/PHP hack, is the biggest kludge I've ever seen - but perhaps one of you has some insight on this.

[edit] One further note - the purpose of this check is to dynamically create the page in question, not just to store the information. Thus, floR's suggestion below won't work.[/edit]

Thanks,

Ben

[floR]

Easy, keep using the Javascript/PHP trick, but from within an IMG tag, something like this:

<script>
function getScreenInfo() {
// gets some screen info
}

document.write('<img src="sendinfo.php?screeninfo='+getScreenInfo()+'">');
</script>

Let sendinfo store the screeninfo and return an image (transparent perhaps).

[bbirney]

Good thinking, floR - only one problem, and I should have mentioned this in my original post. I'm trying to dynamically create the page based on the size of the screen, not just store it. I suppose I could have sendinfo.php stick the data into a cookie that I could then access with the main index.php, but I'm not clear on the concurrency issues with that; in fact, it seems quite likely that the code in my index.php would execute before the cookie ever got set, since sendinfo.php isn't invoked until after the page hits the client.... correct? Thus, it would not be possible for sendinfo.php to give the relevant information to index.php in time for it to dynamically create the page based on the user's screen size.

I'm sure there must be some way to do this, because I see pages optimized for variable screen sizes all the time - though a lot of them don't preserve the back functionality, a few of them do.

[floR]

> it seems quite likely that the code in my index.php would execute before the cookie ever got set, since sendinfo.php isn't invoked until after the page hits the client.... correct? Thus, it would not be possible for sendinfo.php to give the relevant information to index.php in time for it to dynamically create the page based on the user's screen size.

Correct. The php/server has NO way of knowing the screen size on the first hit.
Maybe some hidden frame could send info back and forth so it looks like there's no refreshing, like

---

<script>
document.write('<frameset>');
document.write('<frame src="makepagebasedonscreeninfo.php?screeninfo='+getScreenInfo()+'">');
document.write('</frameset>');

</script>

[bbirney]

Now that is a good idea. That will solve my problem quite elegantly. Thanks for the assist!

Ben