php 产生验证码

<?php 
//Session保存路径
$sessSavePath = dirname(__FILE__)."/data/sessions/";
if(is_writeable($sessSavePath) && is_readable($sessSavePath)){ 
    session_save_path($sessSavePath);
}
$letter = "";
//获取随机数字
for ($i=0; $i<3; $i++) {
  $letter .= chr(mt_rand(48,57));
}
//获取随机字母
for ($i=0; $i<3; $i++) {
  $letter .= chr(mt_rand(65,90));
}
//重构字符顺序
$strs = str_split($letter);
shuffle ($strs);
$rndstring = "";
while (list (, $str) = each ($strs)) {
  $rndstring .= $str;
}
//获取随机字符
//$letras = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
//for($i=0; $i<6; $i++) {
    //$rndstring .= chr(mt_rand(48,90));
//  $rndstring .= $letras[rand(0, 35)];
/