[Resolved] My GET/POST dilema

Davidc316

Ok. Let me set the scene...

I'm building a simple online database (non commercial by the way!) that contains information about different cars. When the user enters the site, he will be able to search the database via a simple HTML form which contains drop down menus, textfields and so on.

OK, so let's say that the user decides to view all cars that have a top speed of greater than 150mph. Well... after selecting that option from a drop down, they are taking to a page that displays the results (Google style). On this particular site, each result will be previewed with a small picture and a brief description. The user can then click on one of the small pictures (or sub titles) and will then be taken to a page that shows a full and detailed description of the car.

Ok, that's all pretty standard stuff that I'm sure you've seen before. The trouble is... when I'm creating the HTML form for doing the searches, it doesn't matter whether I use GET or POST- both methods are riddled with problems. I describe a couple of these problems as follows...

A PROBLEM WITH POST:
When you do an initial search, then click to view a page that contains full car details, all is well. BUT, when you click back on your browser the screen goes white and you get a "postnotcached" error.

You can of course, solve this problem by forcing the user to do a screen refresh, but to me that is not acceptable.

A PROBLEM WITH GET:
I must admit, GET, at first glance, seems more promissing than POST, but a closer look has revealed that like POST, it also comes with its own bag of problems. The main one being....

When you do a search using the form (using GET this time), then view the results, then zoom into a specific item page...all is well, at first. BUT, when you go back to the form and try an entirely new search, the results page ALWAYS shows you the same results that you had for the first search that you conducted. This seems to happen regardless of how many screen refreshes you do. Clearly that's being caused because the results page is cached when we use GET. However, just knowing that piece of information does not solve the problem. 🙁

Ok, so that's it. I'm sorry for the long message, but basically I'm totally depressed about GET and POST. It seems that both methods are crap in their own unique ways and I'm just wondering if anyone could offer some advice on this one. I really don't even know which of these two crappy methods I should use.

Thanks!

weekender

what html headers or meta tags are you using? my guess is that the browser is being told not to cache the page, or at least to cache in a different way to the default.

headers showing this will say something like pragma or no-cache

adam

jayant

also an e-tag header.

it should be a header problem only.

Davidc316

Both the search for page and the results page have the following:

<html>
<head>
<title>Untitled Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<script language="JavaScript">

I appreciate the short answers, but this is very important to me so just to spell out what's happening once more...

*When I use POST, I get "postnotcached" errors when I press the back button on my browser.

*When I use GET, the form keeps executing the same search over and over again as if the first search is somehow stored in the cache.

MungoBBQ

Sounds like a caching problem, indeed.

Here's the PHP code I'm using to prevent caching of pages, it works fine in all my applications:

function noCache() {
	header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");    // Date in the past
	header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT"); // always modified
	header("Cache-Control: no-store, no-cache, must-revalidate");  // HTTP/1.1
	header("Cache-Control: post-check=0, pre-check=0", false);
	header("Pragma: no-cache");                          // HTTP/1.0
	}

Include it and use it FIRST on each of your pages you want to prevent caching like so:

<?
include("functions.php"); // Assuming you have nocache function in the file "functions.php"
noCache();
?>
<html>
<head>
... and so forth

Davidc316

You'll not believe this... but that worked- for a minute.

Now it's going back to the old problem of cachying the pages.

Aaaaaaaaaaaaaargghhh!!!

Bascially, I tied your functions trick and it was working ok for a minute or two. But I noticed that on the search results page I was getting a warning at the top of the page that said something like "Can't send cookie, headers already sent".

So, I tried moving the include statement further down the script to where the header info was (the first half of the script is mostly PHP and doesn't generate any output). I thought that maybe this would get rid of my strange cookie warning.

Sure enough, that did indeed get rid of the cookie warning things, BUT now it has gone back to cachying the pages again so I'm getting the same repeating results when I try to execute searches.

I hear you say that the obvious solution is to move the include() stuff back up to the top of the script and get it working ok again. Well... I've tried that and it is STILL cachying the pages.

Don't you just love computers? 🙁

Davidc316

Infact, hang on!

I think I might be onto a solution here...

Give me half an hour to play around with this.

All is well

MungoBBQ

Yes, you have to use the function nocache() before you send any HTML or other output to the browser. Cookies work the same way, so if you just make sure that you send your cookies and use the noCache() function before any other output (this includes blank lines!) you should be fine.

Good luck!

jayant

IE 6 has some major issues regarding this.
some times IE 5, 5,5 also misbehave at this.

perhaps you should try with someother browser firkst. if u dont experience any problems, then best thing to do is, empty all temporary internet files, and then load the page,
and also get updates for IE installed.

Davidc316

Ok. I tried out Mungo's idea and it seems to be working fine now.

The trouble I was having earlier was cos of some session variable thing I had going on. But now that I'm using GET combined with the no-cache trick, there is no need for me to bother with sessions.

So, all is well and thank you!

But just one question... If I set my webpages to no-cache (as suggested above by Mungo), will that use up lots more bandwidth? Most importantly, does this no-cache stuff mean that images on the page will have to be reloaded upon each and every visit????

MungoBBQ

Yes and no. The nocache() should technically only apply to your PHP files, not the images loaded in them. However, since the clients will be forced to reload the pages on each visit they will use up more bandwidth, so only use the function where it is needed.

Davidc316

Thank you Mungo.

You're a credit to this forum!

Thread resolved.