先创建一个demo.php;<img src="imgcode.php" onclick="this.src = ‘imgcode.php?num=‘+new Date().getTime();" />然后创建一个imgcode.php<?phpfunction get_rand_str($length = 4){ $chars = ‘123456789ABCDEFGHJKLMNPQRSTUVWXYZ‘; $str = str_shuffle($chars); // 随机打乱一个字符串 $str = substr($str,0,$length); $str = strtolower($str); return $str;}//验证码图片宽度和高度$width = 45;$height = 18;//新建一张彩色图片$img = imagecreatetruecolor($width,$height);//给这张图片新建两个颜色 //背景颜色$backgroundcolor = imagecolorallocate($img,74,147,223);//文字颜色$textcolor = imagecolorallocate($img,255,255,255);//画一矩形并填充 $width,$height, 对角线imagefilledrectangle($img,0,0,$width,$height,$backgroundcolor);//获取随机数$get_code = get_rand_str(); //获取出来的随机数写到图片上面imagestring($img,5,6,1,$get_code,$textcolor);//防止别人恶意刷验证码在图片上面添加一些点for($i=0;$i<=20;$i++){ $x = mt_rand(0,$width); $y = mt_rand(0,$height); $pxColor = imagecolorallocate($img,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255)); imagesetpixel($img,$x,$y,$pxColor);}//写一个输出图片的声明头信息header("Content-Type:image/png");imagepng($img);//输出完成后销毁imagedestroy($img);?>