Tạo mã random php

****** 1
function rand_string($length) {
$chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 $size = strlen($chars);
 for( $i = 0; $i < $length; $i++ ) {
     $str .= $chars[ rand( 0, $size - 1 ) ];
 }
 return $str;
 }

$my_rand = rand_string(8);


****** 2

function RandomString($len){
    $randstr = '';
    srand((double)microtime()*1000000);
    for($i=0;$i<$len;$i++){
        $n = rand(48,120);
        while (($n >= 58 && $n <= 64) || ($n >= 91 && $n <= 96)){
            $n = rand(48,120);
        }
        $randstr .= chr($n);
    }
    return $randstr;
}

$Test = RandomString(10);