core/Utils.php
public static function randWord($len = 4)
    {
        $chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
        $word = '';
        for ($i = 0; $i < $len; $i++) {
            $word .= $chars[mt_rand(0, strlen($chars) - 1)];
        }
        return $word;
    }
public static function randWord($len = 4)
    {
        $chars = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
        $word = '';
        for ($i = 0; $i < $len; $i++) {
            $word .= $chars[mt_rand(0, strlen($chars) - 1)];
        }
        return $word;
    }
随机字母数字
@param int $len
@return string