生成随机字符串和验证码的类的PHP实例

<?php
class RandCheckCode
{
        /*函数名称:get_code()
        *作用:取得随机字符串
        * 参数:
        1、(int)$length = 32 #随机字符长度
        2、(int)$mode = 0    #随机字符类型，
        0为大小写英文和数字,1为数字,2为小写字母,3为大写字母,
        4为大小写字母,5为大写字母和数字,6为小写字母和数字
        *返回:取得的字符串
        */
        function get_code($length=32,$mode=0)//获取随机验证码函数
        {
                switch ($mode)
                {
                        case '1':
                                $str='123456789';
                                break;
                        case '2':
                                $str='abcdefghijklmnopqrstuvwxyz';
                                break;
                        case '3':
                                $str='ABCDEFGHIJKLMNOPQRSTUVWXYZ';
                                break;
                        case '4':
                                $str='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
                                break;
                        case '5':
                                $str='ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890';
                                break;
                        case '6':
                                $str='abcdefghijklmnopqrstuvwxyz1234567890';
                                break;
                        default:
                                $str='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890';
                                break;
                }
                $checkstr='';
                $len=strlen($str)-1;
                for ($i=0;$i<$length;$i++)
                {
                        //$num=rand(0,$len);//产生一个0到$len之间的随机数
                        $num=mt_rand(0,$len);//产生一个0到$len之间的随机数
                        $checkstr.=$str[$num];

                      
                }
                return $checkstr;
        }

/**     函数名称:create_check_image()
        函数作用:产生一个校验码的图片
        参    数:$checkcode:校验码字符串
        返 回 值:返回该图片
*/
        function create_check_image($checkcode)//产生一个
        {
                $im=imagecreate(65,22);//产生一个图片
                $black=imagecolorallocate($im,0,0,0);//背景颜色
                $white=imagecolorallocate($im,255,255,255);//前景颜色
                $gray=imagecolorallocate($im,200,200,200);
                imagefill($im,30,30,$gray);//在$im图像的坐标30,30(图像左上角为0,0)处用$gray 颜色执行区域填充(即与30,30点颜色相同且相邻的点都会被填充)

                imagestring($im,5,8,3,$checkcode,$white);//用$white颜色将字符串$checkcode画到$im 所代表的图像的8,3坐标处(这是字符串左上角坐标,整幅图像的左上角为0,0),5是字体大小, 字体只能是1,2,3,4或5,使用内置字体
                for ($i=0;$i<120;$i++)
                {
                        $randcolor=imagecolorallocate($im,rand(0,255),rand(0,255),rand(0,255));
                        imagesetpixel($im,rand()%70,rand()%30,$randcolor);//在$im图象上用$randcolor颜色在(rand()%70,rand()%30)坐标(图像左上角为0,0)上画一个点
                }
                header("Content-type:image/png");
                imagepng($im);//以PNG格式将图像输出到浏览器或文件
                imagedestroy($im);//销毁图像$im
        }
}
/*
$randcode=new RandCheckCode();
$checkstring=$randcode->get_code(5,7);
$image=$randcode->create_check_image($checkstring);
echo $image;
*/

?>