建立PHP验证码类文件及调用方式

//验证码类
class ValidateCode {
 private $charset = 'abcdefghkmnprstuvwxyzABCDEFGHKMNPRSTUVWXYZ23456789';//随机因子
 private $code;//验证码
 private $codelen = 4;//验证码长度
 private $width = 130;//宽度
 private $height = 50;//高度
 private $img;//图形资源句柄
 private $font;//指定的字体
 private $fontsize = 20;//指定字体大小
 private $fontcolor;//指定字体颜色
 //构造方法初始化
 public function __construct() {
  $this->font = dirname(__FILE__).'/font/elephant.ttf';//注意字体路径要写对，否则显示不了图片
 }
 //生成随机码
 private function createCode() {
  $_len = strlen($this->charset)-1;
  for ($i=0;$i<$this->codelen;$i++) {
   $this->code .= $this->charset[mt_rand(0,$_len)];
  }
 }
 //生成背景
 private function createBg() {
  $this->img = imagecreatetruecolor($this->width, $this->height);
  $color = imagecolorallocate($this->img, mt_rand(157,255), mt_rand(157,255), mt_rand(157,255));
  imagefilledrectangle($this->img,0,$this->height,$this->width,0,$color);
 }
 //生成文字
 private function createFont() {
  $_x = $this->width / $this->codelen;
  for ($i=0;$i<$this->codelen;$i++) {
   $this->fontcolor = imagecolorallocate($this->img,mt_rand(0,156),mt_rand(0,156),mt_rand(0,156));
   imagettftext($this->img,$this->fontsize,mt_rand(-30,30),$_x*$i+mt_rand(1,5),$this->height / 1.4,$this->fontcolor,$this->font,$this->code[$i]);
  }
 }
 //生成线条、雪花
 private function createLine() {
  //线条
  for ($i=0;$i<6;$i++) {
   $color = imagecolorallocate($this->img,mt_rand(0,156),mt_rand(0,156),mt_rand(0,156));
   imageline($this->img,mt_rand(0,$this->width),mt_rand(0,$this->height),mt_rand(0,$this->width),mt_rand(0,$this->height),$color);
  }
  //雪花
  for ($i=0;$i<100;$i++) {
   $color = imagecolorallocate($this->img,mt_rand(200,255),mt_rand(200,255),mt_rand(200,255));
   imagestring($this->img,mt_rand(1,5),mt_rand(0,$this->width),mt_rand(0,$this->height),&#39;*&#39;,$color);
  }
 }
 //输出
 private function outPut() {
  header(&#39;Content-type:image/png&#39;);
  imagepng($this->img);
  imagedestroy($this->img);
 }
 //对外生成
 public function doimg() {
  $this->createBg();
  $this->createCode();
  $this->createLine();
  $this->createFont();
  $this->outPut();
 }
 //获取验证码
 public function getCode() {
  return strtolower($this->code);
 }
}

<
<form id="login" action="" method="post">
<p>此例为session验证实例</p>
<p>
<span>验证码：</span>
<input type="text" name="validate" value="" size=10> 
<img  title="点击刷新" src="./captcha.php" align="absbottom" onclick="this.src=&#39;captcha.php?&#39;+Math.random();"></img>
</p>
<p>
<input type="submit">
</p>
</form>
<?php
//打印上一个session;
//echo "上一个session：<b>".$_SESSION["authnum_session"]."</b><br>";
$validate="";
if(isset($_POST["validate"])){
$validate=$_POST["validate"];
echo "您刚才输入的是：".$_POST["validate"]."<br>状态：";
if($validate!=$_SESSION["authnum_session"]){
//判断session值与用户输入的验证码是否一致;
echo "<font color=red>输入有误</font>"; 
}else{
echo "<font color=green>通过验证</font>"; 
}
} 
?>