Generate code without guess

Here is something I use.

PHP Code:

   public function generate_code() {
        // generate a randomish code
        $code = bin2hex(pack('N', microtime(TRUE))).bin2hex(get_instance()->security->get_random_bytes(4));
        return $code;
    } 


It was suggested to me here on these forums somewhere by Narf ages ago but I use it all the time on almost every site I do. It is great for generating unique codes for urls, for all sorts of records, rather than using id. I have it in a functions model that has all my useful functions in. You could use more random bytes if you wanted a longer code.

Generates something like: 59aad953a91644ce

Hope it helps,

Paul

PS This is not for security, this is just to generate a code I can use instead of an ID, i.e.

Code:

Not: www.mysite.co.uk/view/record/4
But: www.mysite.co.uk/view/record/59aad953a91644ce

You still have to check it is unique when storing, and when using to retrieve a record that the user has permission to access it.

PHP Code:

/**
 * Generate a random string
 * 
 * @link https://paragonie.com/b/JvICXzh_jhLyt4y3
 *
 * @param int $length - How long should our random string be?
 * @param string $charset - A string of all possible characters to choose from
 * @return string
 */
function random_str($length = 32, $charset = 'abcdefghijklmnopqrstuvwxyz')
{
    // Type checks:
    if (!is_numeric($length)) {
        throw new InvalidArgumentException(
            'random_str - Argument 1 - expected an integer'
        );
    }
    if (!is_string($charset)) {
        throw new InvalidArgumentException(
            'random_str - Argument 2 - expected a string'
        );
    }

    if ($length < 1) {
        // Just return an empty string. Any value < 1 is meaningless.
        return '';
    }
    
    // Remove duplicate characters from $charset
    $split = str_split($charset);
    $charset = implode('', array_unique($split));
    
    // This is the maximum index for all of the characters in the string $charset
    $charset_max = strlen($charset) - 1;
    if ($charset_max < 1) {
        // Avoid letting users do: random_str($int, 'a'); -> 'aaaaa...'
        throw new LogicException(
            'random_str - Argument 2 - expected a string that contains at least 2 distinct characters'
        );
    }
    // Now that we have good data, this is the meat of our function:
    $random_str = '';
    for ($i = 0; $i < $length; ++$i) {
        $r = random_int(0, $charset_max);
        $random_str .= $charset[$r];
    }
    return $random_str;
} 


https://paragonie.com/blog/2015/07/commo...dom-string

https://github.com/paragonie/random_compat

@rtenny, using md5 width a timestamp is not the best idea. Use PaulD code or the random_str from paragonie.