Question

So I was wonder what are some good/preferred methods for generating a ‘hex-like’ value in PHP? Preferably, I would want to restrict it to 5 characters long like such: 1e1f7

Currently this is what I am doing:

echo dechex(mt_rand(10000, 99999));

however this gives me values anywhere from 4-5 characters long, and I want to keep it at a consistent 4 or 5.

What are some ways to better generate something like this in PHP? Is there even a built in function?

Note: When I say ‘hex-like’ I really just mean a random combination of letters and numbers. There does not have to be a restriction on available letters.

Answer 1

Something simple like:

$length = 5;
$string = "";
while ($length > 0) {
    $string .= dechex(mt_rand(0,15));
    $length -= 1;
}
return $string;

(untested)

Or fix your mt_rand range to: mt_rand(65535, 1048575) (10000-fffff in hex) or if you like tinfoil hats: mt_rand(hexdec("10000"), hexdec("ffffff"))

The advantage of the while-loop approach is that it works for arbitrarily long strings. If you’d want 32 random characters you’re well over the integer limit and a single mt_rand will not work.

If you really just want random stuff, I’d propose:

$length = 5;
$string = "";
$characters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-=+!@#$%^&*()[]"; // change to whatever characters you want
while ($length > 0) {
    $string .= $characters[mt_rand(0,strlen($characters)-1)];
    $length -= 1;
}
return $string;

(untested)