php验证码制作

php   $str = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'; ///数字和字母验证码 $str2 = 'ABCDEF0123456789'; ///用于验证码字符，16进制颜色  $captcha=''; ///验证码初始值

////随机获取四个字符的验证码 for ($i=0; $i < 4; $i  ) {     $color = '#';         for ($j=0; $j < 6; $j  ) {              $color.=$str2{      
       mt_rand(0,strlen($str2)-1)};          }
$captcha .= '$color.'">'.$str{      
       mt_rand(0,strlen($str)-1)}.''; }

///输出显示带框的验证码 echo ''.$captcha.''; 
$captcha = strip_tags($captcha); //去除html标签，去除颜色，留下纯字符  echo "
"; echo "
"; echo "
"; 
/* 验证码输入框
 * 设置一个hidden存储验证码的标签值
 * 用post该方法将验证码的值和输入值传输到verify2.php去比较验证
 */ echo<<<EOF     
          $captcha}" />          
 EOF;  ?>

php
  // 将获取到验证码的值和输入值转换为小写，并使用php内置函数srim()去除左右空间     $verify = trim(strtolower($_POST['verify']));      $verify2 = trim(strtolower($_POST['captcha']));
     ///判断输入是否空
  if (!isset($verify) || $verify == '') {         exit('null..try again');     }

  ///判断验证码输入是否成功     if ($verify == $verify2) {         echo "success！";     }else exit('wrong..try again');  ?>