//随机生成字符串
function random($length) {
srand(date("s"));
$possible_charactors = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
$string = "";
while(strlen($string)<$length) {
$string .= substr($possible_charactors,(rand()%(strlen($possible_charactors))),1);
}
return($string);
}