英文同数字 <?php Header("Content-type:image/png"); //定义header，声明图片文件，最好是png，无版权之扰;  //生成新的四位整数验证码 session_start();//开启session; $authnum_session = '';  $str = 'abcdefghijkmnpqrstuvwxyz1234567890';  //定义用来显示在图片上的数字和字母; $l = strlen($str); //得到字串的长度;  //循环随机抽取四位前面定义的字母和数字;  for($i=1;$i<=4;$i++) {  $num=rand(0,$l-1);  //每次随机抽取一位数字;从第一个字到该字串最大长度, //减1是因为截取字符是从0开始起算;这样34字符任意都有可能排在其中; $authnum_session.= $str[$num];  //将通过数字得来的字符连起来一共是四位; } session_register("authnum_session"); //用session来做验证也不错;注册session,名称为authnum_session, //其它页面只要包含了该图片 //即可以通过$_SESSION["authnum_session"]来调用 //生成验证码图片， srand((double)microtime()*1000000); $im = imagecreate(50,20);//图片宽与高;  //主要用到黑白灰三种色; $black = ImageColorAllocate($im, 0,0,0); $white = ImageColorAllocate($im, 255,255,255); $gray = ImageColorAllocate($im, 200,200,200);  //将四位整数验证码绘入图片 imagefill($im,68,30,$gray); //如不用干扰线，注释就行了; $li = ImageColorAllocate($im, 220,220,220); for($i=0;$i<3;$i++)  {//加入3条干扰线;也可以不要;视情况而定，因为可能影响用户输入;  imageline($im,rand(0,30),rand(0,21),rand(20,40),rand(0,21),$li); }  //字符在图片的位置; imagestring($im, 5, 8, 2, $authnum_session, $white); for($i=0;$i<90;$i++) {//加入干扰象素 imagesetpixel($im, rand()%70 , rand()%30 , $gray); } ImagePNG($im); ImageDestroy($im); ?>  中文 <?php     /*     * 文件:code.php     * 作用:验证码生成     */     session_start(); // 设置 content-type     header("Content-type: image/png");     // 创建图片     $im = imagecreatetruecolor(120, 30);      $ChineseChar = array("人","出","来","友","学","孝","仁","义","礼","廉","忠","国","中","易","白","者","火 ","土","金","木","雷","风","龙","虎","天","地",   "生","晕","菜","鸟","田","三","百","钱","福 ","爱","情","兽","虫","鱼","九","网","新","度","哎","唉","啊","哦","仪","老","少","日",   "月 ","星");     // 创建颜色     $fontcolor = imagecolorallocate($im, 255, 255, 255);     $bg = imagecolorallocate($im, 0, 0, 0);     // 设置文字     for($i=0;$i<4;$i++) $text .= $ChineseChar[(array_rand($ChineseChar))];     $_SESSION['code'] = $text; // 设置字体  [url]http://www.font.com.cn/downlist/s_12_3.html[/url] 有_GBK系列的字体下载,一般GD库都支持的! $font = 'gbk.ttf'; // 添加文字     imagettftext($im, 18, 0, 11, 21, $fontcolor, $font, iconv("GB2312","UTF-8",$text));     // 输出图片     imagepng($im);     imagedestroy($im);     ?>