PHP中独特的6位十六进制代码生成器

Question

I am working on a PHP project and i would like to generate an id that is unique and user friendly like the black berry messenger user pin.

It would best prefer if it was six characters long

Is there any algorithm or a combination of PHP functions i can use? if not what is my best bet? Am a newbie.

Answer 1

Lowercase:

sprintf('%06x', mt_rand(0, 16777215))

Uppercase:

sprintf('%06X', mt_rand(0, 16777215))

^(demo)

Reference:

• mt_rand()
• sprintf()

16777215 is 16⁶-1. It's likely that you'll get dupes so you need to store previous values somewhere (typically a database) and check for uniqueness.

Another solution is to generate all 17 million codes at once, shuffle them and pick one each time.

First time:

$all_codes = range(0, 16777215);
shuffle($all_codes);

$sql = 'INSERT INTO all_codes (id, code, taken) VALUES (?, ?, ?)';
foreach ($all_codes as $index => $code) {
    $values = [
        $index+1,
        sprintf('%06X', $code),
        false
    ];
    $your_database_library->query($sql, $values);
}

This script is pure non-optimised brute force so you'll need to increase PHP memory limit (it needs like half GB) but it's a one-time task.

Then, every time you need a code (let's assume MySQL):

SELECT id, code
FROM all_codes
WHERE used = 0
ORDER BY 1
LIMIT 1
FOR UPDATE;

UPDATE all_codes
SET used = 1
WHERE id = ?;

Alternatively, you could store them in sequence and pick randomly among the unused, making sure to implement a solution that's fast in your DBMS (because you're randomising every time) but that looks like more work :)