$(function() {

    $("#getcode_num").click(function() {  //数字验证

         $(this).attr("src", 'code_num.php?' + Math.random());

     });

     $("#chk_num").click(function() {

         var code_num = $("#code_num").val();

         $.post("chk_code.php?act=num", {

             code: code_num

         },

         function(msg) {

             if (msg == 1) {

                 alert("验证码正确！");

             } else {

                 alert("验证码错误！");

             }

         });

     });

     //数字+字母验证

     $("#getcode_char").click(function() {

         $(this).attr("src", 'code_char.php?' + Math.random());

     });

     $("#chk_char").click(function() {

         var code_char = $("#code_char").val();

         $.post("chk_code.php?act=char", {

             code: code_char

         },

         function(msg) {

             if (msg == 1) {

                 alert("验证码正确！");

             } else {

                 alert("验证码错误！");

             }

         });

     });

     //中文验证码

     $("#getcode_zh").click(function() {

         $(this).attr("src", 'code_zh.php?' + Math.random());

     });

     $("#chk_zh").click(function() {

         var code_zh = escape($("#code_zh").val());

         $.post("chk_code.php?act=zh", {

             code: code_zh

         },

         function(msg) {

             if (msg == 1) {

                 alert("验证码正确！");

             } else {

                 alert("验证码错误！");

             }

         });

     });

     //google验证

     $("#getcode_gg").click(function() {

         $(this).attr("src", 'code_gg.php?' + Math.random());

     });

     $("#chk_gg").click(function() {

         var code_gg = $("#code_gg").val();

         $.post("chk_code.php?act=gg", {

             code: code_gg

         },

         function(msg) {

             if (msg == 1) {

                 alert("验证码正确！");

             } else {

                 alert("验证码错误！");

             }

         });

     });

     //算术验证

     $("#getcode_math").click(function() {

         $(this).attr("src", 'code_math.php?' + Math.random());

     });

     $("#chk_math").click(function() {

         var code_math = $("#code_math").val();

         $.post("chk_code.php?act=math", {

             code: code_math

         },

         function(msg) {

             if (msg == 1) {

                 alert("验证码正确！");

             } else {

                 alert("验证码错误！");

             }

         });

     });

 });

 session_start();

 getCode(4,60,20);  

 function getCode($num,$w,$h) {

     $code = "";

     for ($i = 0; $i < $num; $i++) {

         $code .= rand(0, 9);

     }

     //4位验证码也可以用rand(1000,9999)直接生成

     //将生成的验证码写入session，备验证时用

     $_SESSION["helloweba_num"] = $code;

     //创建图片，定义颜色值

     header("Content-type: image/PNG");

     $im = imagecreate($w, $h);

     $black = imagecolorallocate($im, 0, 0, 0);

     $gray = imagecolorallocate($im, 200, 200, 200);

     $bgcolor = imagecolorallocate($im, 255, 255, 255);

     //填充背景

     imagefill($im, 0, 0, $gray);  

     //画边框

     imagerectangle($im, 0, 0, $w-1, $h-1, $black);  

     //随机绘制两条虚线，起干扰作用

     $style = array ($black,$black,$black,$black,$black,

         $gray,$gray,$gray,$gray,$gray

     );

     imagesetstyle($im, $style);

     $y1 = rand(0, $h);

     $y2 = rand(0, $h);

     $y3 = rand(0, $h);

     $y4 = rand(0, $h);

     imageline($im, 0, $y1, $w, $y3, IMG_COLOR_STYLED);

     imageline($im, 0, $y2, $w, $y4, IMG_COLOR_STYLED);  

     //在画布上随机生成大量黑点，起干扰作用;

     for ($i = 0; $i < 80; $i++) {

         imagesetpixel($im, rand(0, $w), rand(0, $h), $black);

     }

     //将数字随机显示在画布上,字符的水平间距和位置都按一定波动范围随机生成

     $strx = rand(3, 8);

     for ($i = 0; $i < $num; $i++) {

         $strpos = rand(1, 6);

         imagestring($im, 5, $strx, $strpos, substr($code, $i, 1), $black);

         $strx += rand(8, 12);

     }

     imagepng($im);//输出图片

     imagedestroy($im);//释放图片所占内存

 }