php 创建验证码方法

php创建验证码方法：

 <?php
     function getVerify($length=4,$sessName='verify'){
         //验证码
         //获取字符串 去除01ol等较难辨认字符
         $chars = "23456789abcdefghijkmnpqrstuvwxyzABCDEFGHIJKLMNPQRSTUVW";
         $chars = str_shuffle($chars);
         $chars = substr($chars, 0, $length);
         //将字符存入session
         $_SESSION[$sessName] = $chars;
         //定义画布大小
         $width = 80;
         $height = 30;
         $image = imagecreatetruecolor($width, $height);

         //定义背景颜色和边框颜色
         $white = imagecolorallocate($image, 255, 255, 255);
         $black = imagecolorallocate($image, 0, 0, 0);

         //用填充矩形填充画布
         imagefilledrectangle($image, 1, 1, $width-2, $height-2, $white);

         //定义验证码颜色
         $verifyColor = imagecolorallocate($image, 15, 164, 80);

         //将字符写入画布
         for($i=0; $i<$length; $i++){
             $size = 18;
             $angle = mt_rand(-12, 12);
             $x = 5 + $i*$size;
             $y = 23;
             $fontfile = 'GEORGIA.TTF';//字体
             $color = $verifyColor;
             $text = substr($chars, $i, 1);
             imagettftext($image, $size, $angle, $x, $y, $color, $fontfile, $text);
         }
         //干扰点
         for($i=0; $i<80; $i++){
             imagesetpixel($image, mt_rand(0, $width-1), mt_rand(0, $height-1), $verifyColor);
         }
         //干扰线
         for($i=0; $i<3; $i++){
             imageline($image, mt_rand(0, $width-1), mt_rand(0, $height-1), mt_rand(0, $width-1), mt_rand(0, $height-1), $verifyColor);
         }
         //告诉浏览器输出格式
         header("content-type:image/gif");
         //输出
         imagegif($image);
         //销毁，释放内存
         imagedestroy($image);
     }