[PHP] openssl_random_pseudo_bytes 関数と Base64_encode 関数を利用してランダムな文字列を生成する

public static function getRandomString($length = 42) {        /* * Use OpenSSL (if available) */        if (function_exists('openssl_random_pseudo_bytes')) {            $bytes = openssl_random_pseudo_bytes($length * 2);            if ($bytes === false)                throw new RuntimeException('Unable to generate a random string');            return substr(str_replace(['/', '+', '='], '', base64_encode($bytes)), 0, $length);        }        $pool = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';        return substr(str_shuffle(str_repeat($pool, 5)), 0, $length);    }

substr(str_shuffle(str_repeat($pool, 5)), 0, $length);