获取随机的字符串

获取随机的字符串，用于token，EncodingAESKey等的生成

function get_rand_char($length = 6) {
$str = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz";
$strLength = 61;

for($i = 0; $i < $length; $i ++) {
$res .= $str [rand ( 0, $strLength )];
}

return $res;
}