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Posted by Dynamo on 05/29/06 11:12
Thanks for that Jerry and others that have posted replies. I guess that because
of the type of work that I am doing that you all assume I am reasonably
proficient in php. Well I can assure you that I am not :(
I am still relatively green and date/time manipiulation in databases has never
been one of my fortes. I get the gist of what you are telling me to do and I
have created a pending transaction table. So now my confirmpurchase.php looks
something like this and I would be grateful if you could cast your eye over and
tell me if this is what you mean plus a little help with $firstquery :
<?php
$id = $_POST['item_number'];
$firstquery = "DELETE FROM Pendingtransactions WHERE time=(any records that are
older than 20mins)";
$result = mysql_query($firstquery) or die ("Failed query of" . $firstquery);
mysql_free_result($result);
$secondquery = "SELECT FROM Pendingtransactions WHERE catid = $id";
$result = mysql_query($secondquery) or die ("Failed query of" . $secondquery);
if (mysql_num_rows($result) > 0) {
echo "Sorry but this item is currently being purchased by somebody else.<br>
If they choose to cancel their sale then this product will become available
again in 20 mins";
}
else {
$thirdquery = "INSERT INTO Pendingtransactions (catid) VALUES ('$id')";
?>
<p align="center"><font face="Arial" size="2"><b>
You have chosen to add the following item to your shopping basket.<br>
Please click Confirm to continue or Cancel to stop your transaction.<br>
Please note that this page will time out in 20 minutes. If you do not<br>
make your purchase within this timescale then the product will become<br>
available again for others to buy.
</b></font></p>
<?php
//Then display item they are purchasing
//and add form to send payment to paypal
//plus form to cancel purchase if they so desire//
//I'm ok with this part
}
?>
Many thanks in advance.
Dynamo
In article <e7idnWgWP4Itw-fZ4p2dnA@comcast.com>, Jerry Stuckle says...
>
>This is a typical problem, especially when working on the web. However, it has
>existed ever since databases started tracking data :-).
>
>One of the worst things you can do is keep this in a session. Session data may
>not be written to the database immediately, causing you to sell the last item
>twice. Additionally, session data is not necessarily cleared from the database
>when the session expires. So you may not be able to sell an item which is
>available.
>
>A database is a good place to keep session data for session data's sake. But
>don't try to use it to access data from another session.
>
>Rather, post the potential sale to a pending transaction table, along with the
>current timestamp. Then have a proc run which goes through the transaction
>table and looks for timestamps older than X minutes (i.e 15 min.- whatever your
>session timeout is). If any are found, add the item back into the inventory and
>remove the entry from the list.
>
>OTOH, if the person completes the sale, remove the item from the pending
>transaction list and place it on a completed order list.
>
>The program which cleans up the pending transaction table can be kicked off via
>a cron job (my favorite way). Another way would be to execute it when someone
>tries to purchase an item. In the latter case I would recommend some type of
>locking action (i.e.an "I am running" entry in a table) to keep more than one
>process from running at the same time.
>
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