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1,生成随机数
用for循环确定生成几个随机数。
用随机函数生成范围内随机数。例如rand(1,15),生成1到15之间的数字。
用16位进制函数把生成数字字母化。dechex(rand(1,15))。
用.=运算来保存几个数字。
把生成好的随机数放到$_SESSION[变量]。等将来跟用户提交的内容比较。
2,创建图片
用图片创建函数确定,所创建的图片大小。
例如$im = imagecreatetruecolor(100,30);其中坐标100,30是以网页左上角为原点,$im为图片变量了。
3,设置颜色
使用函数 创建背景色。例如$bg = imagecolorallocate($im,0,0,0);其中0,0,0是三原色数字,$im为上面创建的图片
使用函数 创建字体色。例如$te = imagecolorallocate($im,255,255,255);
4,把字符写在图像左上角
使用函数 imagestring()吧字符写在图像。例如imagestring($im,5,0,0,$rand,$te);$im为上面创建的图片,5是显示方式,0,0
是坐标,$te是字体颜色
5,输出图像
使用函数 header("Content-type:image/jpeg");imagejpeg($im);输出图像。
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1,开启session功能;例如session_start();
2,写表单
3,表单提交的验证码 数据 与上面的$_SESSION[变量]比较
相等,验证正确。
不相等,则错误。
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