Help with order form to gererate an invoice number

I have just obtained an online merchant account
The bank requires my order forms to create an
Alpha/Numeric code for each order and to pass this
onto their secure credit based card detail { Pay } form
I having problems getting detail from the bank ..
its a pilot program I think
As the bank now puts it
The customer doesn't require any specific invoice
generator or shopping cart
application. All their web site form needs to do is
manage an invoice / customer
reference number that the merchant will use to reconcile
and track his orders.
This number is sent to the payment page and we advise
the merchant is the
payment was successful or not referring back to this
number

I will appreciate any advice
Peter Rice

@chars=("a".."n","p".."z",1..9);
$invoice_num="";
for ($i=1;$i<=10;$i++) {
$invoice_num .= $chars[rand(@chars)];
}
You should see that I didn't use 0 and o on purpose. This should generate a 10 char randomly. You can then keep this $invoice_num and associate it with the proper order. Of course, you need to keep this $invoice_num somwhere so you can keep track of the orders.