Generate a string with random letters and numbers in PHP (UUID)

Question

I created a php code that generates a name with random letters and numbers (like a UUID), something like: 7a299248-fd87-4c42-b37d-a6e50a360d10. But I see that it does not perform well in relation to code execution! How can I improve performance?

$filename = substr(md5(time() . rand(1, 9999)), 0, 8)
    . "-" . substr(md5(time() . rand(1, 9999)), 0, 4)
    . "-" . substr(md5(time() . rand(1, 9999)), 0, 4)
    . "-" . substr(md5(time() . rand(1, 9999)), 0, 4)
    . "-" . substr(md5(time() . rand(1, 9999)), 0, 10);

Answer 1

Assuming you want to generate a UUID, this code only works in PHP 7 or higher

random_bytes - Generates cryptographically secure pseudo-random bytes

function uuid(){
    $data = random_bytes(16);
    $data[6] = chr(ord($data[6]) & 0x0f | 0x40); 
    $data[8] = chr(ord($data[8]) & 0x3f | 0x80); 
    return vsprintf('%s%s-%s-%s-%s-%s%s%s', str_split(bin2hex($data), 4));
}

or: https://github.com/ramsey/uuid