PHP生成随机字符串

<?php
/* Generate Password
* Length : 8
*/
$str = “0123456789abcdefghijklmnopqrstuvwxyz”;   //   输出字符集
$n = 8;   //   输出串长度
$len = strlen($str)-1;
for($i=0 ; $i<$n; $i++){
$s .=  $str[rand(0,$len)];
}
echo $s . “<br/>”;
?>