Server cache?

ChetUbetcha

I had people using a program I wrote and they were having errors returned to them. I had recently cleared my local cache and noticed everything worked fine. Theirs did too, once they cleared their server cache. Should I put in an expiration header tag to make sure the page reloads without cache?

Also, is there a possibility there is server cache causing problems as well? When I'm developing other programs using the same web server and MySQL, albeit different databases, people start getting errors that certain tables do not exist. The error usually refers to a table in the program I am working on, not the one they are using for another program. How can I set up the web server to not cache any information? I think that would alleviate the table does not exist error, but do not know how to set up the server for this.

ixalmida

I doubt it would hurt. The only issue is where you put the headers, since you don't want them to interfere with any other header() functions. I occasionally use the following:

header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Cache-Control: no-cache");
header("Pragma: no-cache");

However, there is no guarantee this will always work in every situation. Part of the problem resides in the client settings, and part is in your server setup (and also any proxies, of course).

With my Apache server config, I find that setting I.E. caching to "automatic" always gives me the newest page I've uploaded. You might consider turning off page caching on the client if you have the speed and bandwidth available to you.

ChetUbetcha

ixalmida;10890730 wrote:

header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Cache-Control: no-cache");
header("Pragma: no-cache");

That's exactly what I was talking (writing) about. Would the header information take care of all the client machines running the program though (as you were mentioning page caching on the client)? I am on an Intranet, so I don't have to worry about speed or bandwidth.

I don't have access to the server and it's running IIS. Is there a setting I could ask them to change?

ixalmida

Would the header information take care of all the client machines running the program though (as you were mentioning page caching on the client)?

The answer is: "It depends." There are a lot of variables here. Some browsers ignore certain headers. The web server may block certain headers. Some proxy servers are going to cache pages no matter what headers you have, unless you happen to also administer those proxy servers and can change settings for your domain.

So the only thing I can tell you is to give it a try. But I would also - at a minimum - ask users to set their browsers caching to "automatic".

ChetUbetcha

I checked the default settings for client machines and the system settings are all forced to automatic, so that's a start in the right direction. Hopefully the header tags will clear up the other issues. One other question...

The users have a form page that submits to another to run the update/modify database. The header tags placed on the form page should take care of the cache - if they are not ignored, as you mentioned could possibly happen. If I were to place that on the next page (update/modify after submit is clicked) that would wipe out what they were sending, correct?

ixalmida

Depending on how you have your submittal process set up, you may not need to expire pages. If the submittal page is all PHP then the client browser isn't going to cache any of it, so you wouldn't even need expire headers. The entire page is processed by the server.

But to answer your question, no - expiring a page would not erase any POST values you send to it. The only thing it will do is make sure that any previous copies stored in the user's cache are ignored. New variables will still be processed.

ChetUbetcha

Well, I tried expiring the page and that did not work. I am currently working on another program which uses the same database server and people who are using program_a are now getting table does not exist with the new program name. I was out the last two days and a couple people said they only got the error once or twice, since I was not in programming on the server. Any new information that might help?