直接上程式碼：

function getRandomString($len, $chars=null)
{
    if (is_null($chars)) {
        $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    }
    mt_srand(10000000*(double)microtime());
    for ($i = 0, $str = '', $lc = strlen($chars)-1; $i < $len; $i++) {
        $str .= $chars[mt_rand(0, $lc)];
    }
    return $str;
}
 

只需呼叫函式 並傳參2即可。

echo getRandomString(2);

 echo chr(mt_rand(65, 90);

大寫字母

 echo chr(mt_rand(97, 122));