PHP7 random number

Code Snippets
#1

I have the following snippet, using PHP7’s random_bytes function:
<?php $bytes = bin2hex(random_bytes(11)) ?>
<?= $bytes ?>
It works and generates a 22-char string, changing to another string every time I refresh the page.
But I have two problems:
(1) a typical output is something like: df17b533def6ab919542a5 ?>
How do I get rid of the trailing " ?>" which appears every time?
(2) the string is of numbers and lowercase letters.
I would prefer a mixture of uppercase, lowercase, and numbers.
How can the code be changed to produce this?

#2

1.) perhaps try terminating your line(s).

1 Like
#3

Thank you. I assume by “terminating your lines” you meant to put a “;” before the ?>

Do you have any ideas for 2)??

#4

Well not sure if the HEX value returned will EVERY have UPPERCASE letters…

So you would have to maybe maybe make your own functions and randomly select a few characters and make them upprecase.

Or perhaps generate your own:

$permitted_chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';

function generate_string($input, $strength = 16) {
    $input_length = strlen($input);
    $random_string = '';
    for($i = 0; $i < $strength; $i++) {
        $random_character = $input[mt_rand(0, $input_length - 1)];
        $random_string .= $random_character;
    }

    return $random_string;
}

// Output: iNCHNGzByPjhApvn7XBD
echo generate_string($permitted_chars, 20);

// Output: Jp8iVNhZXhUdSlPi1sMNF7hOfmEWYl2UIMO9YqA4faJmS52iXdtlA3YyCfSlAbLYzjr0mzCWWQ7M8AgqDn2aumHoamsUtjZNhBfU

echo generate_string($permitted_chars, 100);

More info generating random/secure numbers/strings:

#5

What is your use case for doing this?

#6

My “use case” is this:
I want to generate a “Unique ID number” without using MySQL (or any other RDBM):
– uniqueness is desirable, but not absolutely essential
– I found this code on StackOveflow:

<?php $bytes = bin2hex(random_bytes(11)) ?> <?= $bytes ?>

which uses PHP7 (I am using PHP7.2) to generate a (fairly) random number, and I am relying on the 22-char length of the generated hex value to make it unlikely to create duplicate values for the few thousands of times I expect it to be used.
(I could in future add code to check against an existing list of values and regenerate in case of duplication).
I thought that a mixture of upper & lowercase letters (plus numbers) would look better and maybe give a wider range of values, but i’m not sure if that can be done without greatly complicating what is after all a very simple piece of code which works albeit without uppercase!!

#7

The randomness is provided by random_bytes; bin2hex - or any other encoding function - is just representation. Using more characters won’t give you more randomness.

#8

You didn’t give me a use case. You just told me what you are trying to do which I already knew. What is this random number used for? Why are you trying to do this?

#9

I have some form-to-email php code which sends an email to me when a visitor to my website clicks “Submit” having completed some form fields on my webpage.
What I need is a unique id which can be generated at the time of “Submit”, which I can use to identify multiple submissions from each other.

#10

Its not for security reasons/encryption… and just personal, internal tracking issues, then why bother?

or use the similar approach I posted above where you generate your OWN output with the lower and upper case characters.

#11

I was hoping in my ignorance that someone would say “add xxxx” and you’d get what you want.
Thanks for your help, but I was really trying to keep it simple!!
Stay safe.

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