make a unique, random number to use as an order ID - php

Question

I'm working right now to get a unique order number for the item being purchased.
The problem is such that I have payment gateway at quickpay and it comes up and says this: "Error in field: ordernumber"
I have tried to make it like this:
$idag = date("dmY");
$a = substr(str_shuffle('abcdefghijklmnopqrstuvwxyz#!*_-?>/+,ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'), 0, 4);
$total = $idag . $a;
$sql = "SELECT pakker.pris FROM pakker WHERE pakker.id = 3";
if ($stmt = $this->mysqli->prepare($sql)) {
$stmt->execute();
$stmt->bind_result($pris);
while ($stmt->fetch()) {
$protocol = '7';
$msgtype = 'authorize';
$merchant = '89898978';
$language = 'da';
$ordernumber = $total;// here must order number came up.
I have also tried to do it like this.
$idag = date("dmY");
$rand = strtoupper(substr(uniqid(sha1(time())), 0,8));
$a = substr(str_shuffle('abcdefghijklmnopqrstuvwxyz#!*_-?>/+,ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'), 0, 4);
$total = $idag . $a . $rand;

Answer 1

From the [API documentation for Quickpay]:
ordernumber
/^[a-zA-Z0-9]{4,20}$/
A value by merchant's own choice. Must be unique for each transaction. Usually an incrementing sequence. The value may be reflected in the your bank account list.
You need to alter your random order ID generator to exclude any non-alphanumeric characters.
i.e.
$idag = date("dmY");
$a = substr(str_shuffle('abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'), 0, 4);
$total = $idag . $a;
if I were you, I'd use the unix timestamp and then add a few extra characters to the end.