在PHP中创建长度为5的唯一ID

Question

I know the uniqid() method to create lots of unique ids with a length of 7 or more, but what I want to create is a length of 5 unique id with no collision.

Is it possible to create 220.000 unique id's with a length of 5 and check if there is any collision?

Answer 1

You can try

for($i = 0; $i < 10 ; $i++)
{
    echo randString(5),PHP_EOL ;
}

Output

7fh96
G93fd
97Q7E
90Wku
7Vby9
4678f
S11oe
67688
19D36
KC1bQ

Simple Collision Test

$hash = array();
$collision = 0;
while ( count($hash) < 220000 ) {
    $r = randString(5);
    if (isset($hash[$r])) {
        $collision ++;
        continue;
    }
    $hash[$r] = 1;
}

print(($collision / 220000)  * 100 . "% - ($collision)");

Tested 100,000 times and always collision is always less that 0.02 which makes the function efficient for a 5 character set

0.011818181818182% - (26)

Function Used

function randString($length) {
    $char = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    $char = str_shuffle($char);
    for($i = 0, $rand = '', $l = strlen($char) - 1; $i < $length; $i ++) {
        $rand .= $char{mt_rand(0, $l)};
    }
    return $rand;
}