mysql_select_db

Anon

Is there a way to get the name of the currently selected database? Or to perform a query in a separate database without changing the database that the current link identifier points to?

I'm writing a function that can be included in any page, that does some database work. It must not alter the current database pointer for the page it is included in, or if it does change it, it must put it back as it found it when the function completes.

[deleted]

Simple solution: the script that includes this function knows wich database it should use, so it can send that name along to the function. The function can then switch to whatever database it needs, and when it's finished it can switch back to the database it got from the 'parent' script.

Note that MySQL is one of the very few databases that allows switching to another databse. Most databases let you connect to onw database at a time (which makes sense)

Anon

I wish it were that simple. The code is for a banner management system and the function is to display the correct banner on the page.

I have a written a page in the back end system that will generate the php code that will include the function from another file and then call it. This code can be cut-and-pasted into whatever page, which may or may not already have a database connection set up.

I might just end up having to manually add another mysql_select_db call with whatever database name if it is needed on the calling page, on a per page basis, if I can't code it automatically.

It's funny that there's not a function in sql to get the name of the currently select db though.

[deleted]

In that case, you can't use a database switch, and you must make the banner script open it's own database connection.

A forum, a FAQ, what else do you need?

Time to YAPF!: http://www.hvt-automation.nl/yapf/

[deleted]

... and make sure you NEVER EVER EVER use the default connection, Always define which connection you want to use, or you will serious ly f*ck up any script that happens to use the default connection (and most scripts do because few people bother to use connection names)

A forum, a FAQ, what else do you need?

Time to YAPF!: http://www.hvt-automation.nl/yapf/

Anon

Opening a new connection for the banner function won't solve the problem. I can open a new connection within the function:
$forbanner=db_connect...
but then all of my pages use mysq_query($sql)
rather than mysql_query($sql,$db) - you see - they will all default to the last opened connection - which would be the one to the banner database. This is where me saving a few characters in my code comes back to haunt me - short of going back through and changing every page that has database access I don't think there's a way round it.

[deleted]

"This is where me saving a few characters in my code comes back to haunt me "

Told you so :-)

Another thing you could do is link the banner in as an image tag:
<img src=banner.php?parameters>

then the script will be started as a seperate request, with it's own connections etc, not f*cking up your main script anymore.

Anon

Thanks, thats potentially a good idea, only problem is there's not always going to be a banner that will be displayed - in which case I don't want to print an image out.

[deleted]

There's always something isn't there? :-)

How about just printing a one-pixel gif?

Anon

Hmm, hardly elegant, but it is a solution. Just to complicate matters further, some pages need two banners where as some only need one. On the pages that have two banners I need to avoid displaying the same one twice. To get round the problem I have a static var (banner) within the function that is the filename of the banner that has been printed out. The sql query in the function that selects the banners is something like "select * from banners where filename!='$banner'"
- you see? On pages where there are two banners selected the first time the function is called banner is not selected so all available banners are returned. On the second call the static var banner is set so the banner that was displayed is not selected as a potential candidate.

Now of course if I moved the code to a separate page this would stop working.

I don't really excpect you to help me with a solution for this, I was just letting you know how complicated it is!
Thanks for all your help/suggestions Vincent

[deleted]

"I don't really excpect you to help me with a solution for this,"

...but it would be nice? :-)

You could use an extra table in the database that just holds the client's IP ($HTTP_SERVER_VARS['REMOTE_HOST']) and the banners that were displayed, and when they were displayed:

IP | bannerid | timestamp

Then re-program your banner script to look at this table and see which banners have been displayed to this client in the last X seconds/minutes/hours/days/whatever.
You can then exclude those banners from the choice for the next banner. The choice that is made can then be added to the database so that the next banner script will not choose the same banner.

With carefull pummeling you can do all that in one query, but some sort of locking might be in order due to the high concurrency of the banner requests.

Just remember to clean out the old unwanted data every now and then.

A forum, a FAQ, what else do you need?