<?php
	session_start();
if(isset($_POST['dosubmit'])) {
	if(strtoupper($_SESSION['code']) == strtoupper($_POST['code']) ) {
		echo "输入成功!<br>";
	}else{
		echo "输入不对!<br>";
	}
}
?>

<body>
	<form action="reg.php" method="post">
		username: <input type="text" name="username"> <br>
		password: <input type="password" name="password"> <br>
		code: <input type="text" οnkeyup="if(this.value!=this.value.toUpperCase()) this.value=this.value.toUpperCase()" size="6" name="code"> 
		      <img src="code.php" οnclick="this.src='code.php?'+Math.random()" />  <br>

		<input type="submit" name="dosubmit" value="登 录"> <br>
		
	</form>
</body>

<?php
	//开启session
	session_start();
	include "vcode.class.php";
	//构造方法
	$vcode = new Vcode(80, 30, 4);
	//将验证码放到服务器自己的空间保存一份
	$_SESSION['code'] = $vcode->getcode();
	//将验证码图片输出
	$vcode->outimg();


<?php
	class Vcode {
		private $width;    //宽
		private $height;   //高
		private $num;	   //数量
		private $code;    //验证码
		private $img;     //图像的资源
		//构造方法， 三个参数
		function __construct($width=80, $height=20, $num=4) {
			$this->width = $width;
			$this->height = $height;
			$this->num = $num;
			$this->code = $this->createcode(); //调用自己的方法
		}
		//获取字符的验证码， 用于保存在服务器中
		function getcode() {
			return $this->code;
		}
		//输出图像
		function outimg() {
			//创建背景 (颜色， 大小， 边框)
			$this->createback();
			//画字 (大小， 字体颜色)
			$this->outstring();
			//干扰元素(点， 线条)	
			$this->setdisturbcolor();
			//输出图像
			$this->printimg();
		}
		//创建背景
		private function createback() {
			//创建资源
			$this->img = imagecreatetruecolor($this->width, $this->height);
			//设置随机的背景颜***gcolor =  imagecolorallocate($this->img, rand(225, 255), rand(225, 255), rand(225, 255)); 
			//设置背景填充
			imagefill($this->img, 0, 0, $bgcolor);
			//画边框
			$bordercolor =  imagecolorallocate($this->img, 0, 0, 0);
			 imagerectangle($this->img, 0, 0, $this->width-1, $this->height-1, $bordercolor);
		}
		//画字
		private function outstring() {
			for($i=0; $i<$this->num; $i++) {
				$color= imagecolorallocate($this->img, rand(0, 128), rand(0, 128), rand(0, 128)); 
				$fontsize=rand(3,5);  //字体大小
				$x = 3+($this->width/$this->num)*$i; //水平位置
				$y = rand(0, imagefontheight($fontsize)-3);
				//画出每个字符
				imagechar($this->img, $fontsize, $x, $y, $this->code{$i}, $color);
			}
		}
		//设置干扰元素
		private function setdisturbcolor() {
			//加上点数
			for($i=0; $i<100; $i++) {
				$color= imagecolorallocate($this->img, rand(0, 255), rand(0, 255), rand(0, 255)); 
				imagesetpixel($this->img, rand(1, $this->width-2), rand(1, $this->height-2), $color);
			}
			//加线条
			for($i=0; $i<10; $i++) {
				$color= imagecolorallocate($this->img, rand(0, 255), rand(0, 128), rand(0, 255)); 
				imagearc($this->img,rand(-10, $this->width+10), rand(-10, $this->height+10), rand(30, 300), rand(30, 300), 55,44, $color);
			}
		}
		//输出图像
		private function printimg() {
			if (imagetypes() & IMG_GIF) {
   				 header("Content-type: image/gif");
    				imagegif($this->img);
			} elseif (function_exists("imagejpeg")) {
   				 header("Content-type: image/jpeg");
   				 imagegif($this->img);
			} elseif (imagetypes() & IMG_PNG) {
   				 header("Content-type: image/png");
    				imagegif($this->img);
			}  else {
  				  die("No image support in this PHP server");
			} 
		}
		//生成验证码字符串
		private function createcode() {
			$codes = "3456789abcdefghijkmnpqrstuvwxyABCDEFGHIJKLMNPQRSTUVWXY";
			$code = "";
			for($i=0; $i < $this->num; $i++) {
				$code .=$codes{rand(0, strlen($codes)-1)};	
			}
			return $code;
		}
		//用于自动销毁图像资源
		function __destruct() {
			imagedestroy($this->img);
		}
	}