Counter problems

Anon

I want to do something really easy, but after 4 hours of hacking away at it I don't seem to be able to find the answer.

Every time someone uses a simple PHP took I have, they click submit, I just want this to add one to a table, for example my table is called score_calc_useage, and has one field, a largeint called useage. So upon clicking submit, 1 should be added, I can't get it though.

Below is what I've got, I've tried setting a $useage variable of $useage + 1 and similar, but I can't read the current number from the database, if I can get that out somehow, into a variable with I can then just add one to and insert back I'd be sorted!

<?php
include "connect.inc";
$result = mysql_query("SELECT * FROM score_calc_useage",$db);

do {

printf ("%s\n", $myrow["useage"]);

} while ($myrow = mysql_fetch_array($result));

if ($submit) {

$sql = "UPDATE score_calc_useage SET useage='$useage + 1'";
$result = mysql_query($sql);

mysql_close();
}

<FORM ACTION="<?php echo($PHP_SELF); ?>" METHOD=POST>
<INPUT TYPE=SUBMIT NAME="submit" VALUE="SUBMIT">
</FORM>

Thanks for any help.

polson

Awhile ago I made a simple "hit counter" , it is heavily commented and meant to "teach" people what it's doing. Check it out here :

http://evilwalrus.com/viewcode.php?codeEx=189

Regarding your script above, the value of $useage is never defined (gotten) so I assume your counter is stuck at '1' , right?

Check out the "hit counter" link, it should explain one way to do it. That and I am too lazy to write more useful words ;-)

kparker

So it's just as easy to write non-multi-user-safe code using a dbms as it is with text files?

At least if you wrote the update query as

   UPDATE $dbtable SET hits = hits+1 WHERE url='$url'

i.e. let MySql do the incrementing instead of doing in your php script, then the accumulated count would be correct in the presence of simultaneous updates to the same url's record, even though the displayed value of the hit counter might show the same value for any number of simultaneous connections.

To make things accurate in display as well, using MySql you (unfortunately) must lock the entire table. In a more fully-featured dbms (e.g. PostgreSQL) you can merely say:

   begin;
   select ..... FOR UPDATE;
   update ...
   end;

and block simultaneous access to the same row only, rather than the entire table.

Anon

Actually if I'm reading the New Riders
MySQL book right it assures locking is
unnecessary as LAST_INSERT_ID() will
be client specific and return the value
it set FOR YOUR UPDATE...

Hope this helps...

-JAS