Random string rules - php

Question

I have a function that generates a random 3-character alpha-numeric string. I need to modify it in such a way that the new string consisted of 2 alpha and 2 numeric characters. The combination of numbers and letters can be random.
function generate_random($length = 3) {
$characters = '123456789ABCDEFGHJKLMNPRSTUVWXYZ';
$rand_str = '';
for ($p = 0; $p < $length; $p++) {
$rand_str .= $characters[mt_rand(0, strlen($characters)-1)];
}
return $rand_str;
}
I need to modify it in such a way that the new string consisted of 2 alpha and 2 numeric characters. The combination of numbers and letters can be random. How do I do that?

Answer 1

I would personally do it this way:
function generate_random($countAlpha = 2, $countNumeric = 2, $randomize = true) {
$alpha = 'ABCDEFGHJKLMNPRSTUVWXYZ';
$numeric = '123456789';
$rand_str = '';
for ($p = 0; $p < $countAlpha; $p++) {
$rand_str .= $alpha[mt_rand(0, strlen($alpha)-1)];
}
for ($p = 0; $p < $countNumeric; $p++) {
$rand_str .= $numeric[mt_rand(0, strlen($numeric)-1)];
}
if($randomize) {
$rand_str = str_split($rand_str);
shuffle($rand_str);
return implode($rand_str);
}
return $rand_str;
}
Inside I have 2 for loops, each one based on parameters $countAlpha and $countNumeric. I also have a 3rd parameter, $randomize that will allow you to randomize the output if you wish.

Answer 2

You could separe numbers and letter. Then, append N values of each into an array, shuffle it, and the implode to get your string:
function generate_random($nNumbers = 2, $nAlpha = 2) {
// prepare data to use
$num = '123456789';
$numlen = strlen($num) - 1;
$alpha = 'ABCDEFGHJKLMNPRSTUVWXYZ';
$alphalen = strlen($alpha) - 1;
$out = []; // New array
// generate N numbers
for ($i = 0; $i < $nNumbers ; $i++) {
$out[] = $num[mt_rand(0, $numlen)];
}
// generate N letters
for ($i = 0; $i < $nAlpha ; $i++) {
$out[] = $alpha[mt_rand(0, $alphalen)];
}
shuffle($out); // Shuffle the array
return implode($out); // Convert to string
}
echo generate_random() ;
// echo generate_random(2, 4) ; // example