how to write prefixed unique coupon code in php - php

Question

I am trying to write prefixed unique coupon code for get the chance to be a intern at one company. It went well so far, my code is generating 250st, 10 length of codes every time I refresh the page. However, I am issuing a problem with prefixed part. Normally coupon code is looking like this, just one example "1SC476XY3B" but I want every code to start "AB" and then 8 length of code so total will be 10. Can you help me guys? All help will be appreciated, thanks.
<?php
function unique_coupon_codes($number_of_codes,$exclude_codes_array='',$code_length = 10)
{
$characters = "0123456789QWERTYUIOPASDFGHJKLZXCVBNM";
$unique_codes = array();
for($j = 1 ; $j <= $number_of_codes; $j++)
{
$code = "";
for ($i = 1; $i <= $code_length; $i++)
{
$code .= $characters[mt_rand(0, strlen($characters)-1)];
}
if(!in_array($code,$unique_codes))
{
if(is_array($exclude_codes_array))
{
if(!in_array($code,$exclude_codes_array))
{
$unique_codes[$j] = $code;
}
else
{
$j--;
}
}
else
{
$unique_codes[$j] = $code;
}
}
else
{
$j--;
}
}
return $unique_codes;
}
echo '<h1>Unique Coupon Codes</h1>';
echo '<pre>';
print_r(unique_coupon_codes(250,'',10));
echo '</pre>';

Answer 1

It needs a minor change while initializing $code variable. Change $code = ""; to $code = "AB"; And call unique_coupon_codes function as
print_r(unique_coupon_codes(250, '', 8));
Here generate a unique code of 8 digits as you already have prefix AB of length 2 characters.

Answer 2

How about something like this? :-)
function unique_coupon_codes($number_of_codes,$exclude_codes_array=[],$code_length = 10, $code_prefix="") {
$characters="0123456789QWERTYUIOPASDFGHJKLZXCVBNM";
$unique_codes = array();
for($i=1;$i<=$number_of_codes;$i++) {
$code="";
for($o=1;$o<=$code_length;$o++) {
$code .= $characters[mt_rand(0, strlen($characters)-1)];
}
if(in_array($code, $unique_codes) || in_array($code, $exclude_codes_array)) {
$i--;
} else {
$unique_codes[$i] = $code_prefix.$code;
}
}
return $unique_codes;
}
echo '<h1>Unique Coupon Codes</h1>';
echo '<pre>';
print_r(unique_coupon_codes(250,'',8, 'AB'));
echo '</pre>';