php 验证码

学习地址：http://www.imooc.com/video/2458

<?php 
/**
 * 生成验证码
 * @param int $type
 * @param int $length
 * @return string
 */
function buildRandomString($type=1,$length=4){
    if ($type == 1) {
        $chars = join ( "", range ( 0, 9 ) );
    } elseif ($type == 2) {
        $chars = join ( "", array_merge ( range ( "a", "z" ), range ( "A", "Z" ) ) );
    } elseif ($type == 3) {
        $chars = join ( "", array_merge ( range ( "a", "z" ), range ( "A", "Z" ), range ( 0, 9 ) ) );
    }
    if ($length > strlen ( $chars )) {
        exit ( "字符串长度不够" );
    }
    $chars = str_shuffle ( $chars );
    return substr ( $chars, 0, $length );
}


//通过GD库做验证码
function verifyImage($type=1,$length=4,$pixel=0,$line=0,$sess_name = "verify"){
    session_start();
    //创建画布
    $width = 80;
    $height = 28;
    $image = imagecreatetruecolor ( $width, $height );
    $white = imagecolorallocate ( $image, 255, 255, 255 );
    $black = imagecolorallocate ( $image, 0, 0, 0 );
    //用填充矩形填充画布
    imagefilledrectangle ( $image, 1, 1, $width - 2, $height - 2, $white );
    $chars = buildRandomString ( $type, $length );
    $_SESSION [$sess_name] = $chars;
    //$fontfiles = array ("MSYH.TTF", "MSYHBD.TTF", "SIMLI.TTF", "SIMSUN.TTC", "SIMYOU.TTF", "STZHONGS.TTF" );
    $fontfiles = array ("SIMYOU.TTF" );
    //由于字体文件比较大，就只保留一个字体，如果有需要的同学可以自己添加字体，字体在你的电脑中的fonts文件夹里有，直接运行输入fonts就能看到相应字体
    for($i = 0; $i < $length; $i ++) {
        $size = mt_rand ( 14, 18 );
        $angle = mt_rand ( - 15, 15 );
        $x = 5 + $i * $size;
        $y = mt_rand ( 20, 26 );
        $fontfile = "../fonts/" . $fontfiles [mt_rand ( 0, count ( $fontfiles ) - 1 )];
        $color = imagecolorallocate ( $image, mt_rand ( 50, 90 ), mt_rand ( 80, 200 ), mt_rand ( 90, 180 ) );
        $text = substr ( $chars, $i, 1 );
        imagettftext($image, $size, $angle, $x, $y, $color, "", $text);

    }
    if ($pixel) {
        for($i = 0; $i < 50; $i ++) {
            imagesetpixel ( $image, mt_rand ( 0, $width - 1 ), mt_rand ( 0, $height - 1 ), $black );
        }
    }
    if ($line) {
        for($i = 1; $i < $line; $i ++) {
            $color = imagecolorallocate ( $image, mt_rand ( 50, 90 ), mt_rand ( 80, 200 ), mt_rand ( 90, 180 ) );
            imageline ( $image, mt_rand ( 0, $width - 1 ), mt_rand ( 0, $height - 1 ), mt_rand ( 0, $width - 1 ), mt_rand ( 0, $height - 1 ), $color );
        }
    }
    header ( "content-type:image/gif" );
    imagegif ( $image );
    imagedestroy ( $image );
}

网上找到的不错的验证码：http://www.jb51.net/article/40341.htm

需要下载字体：elephant.ttf

html使用：<img  title="点击刷新" src="./captcha.php" align="absbottom" onclick="this.src='captcha.php?'+Math.random();"></img>

<?php 
session_start();
//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,$this->height),'*',$color);
  }
 }
 //输出
 private function outPut() {
  header('Content-type:image/png');
  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);
 }
}

//使用方法，通常是在另一个单独的php页面执行的：
/*
$_vc = new ValidateCode(); 
$_vc->doimg();  
$_SESSION['ValidateCode'] = $_vc->getCode();//验证码保存到SESSION中
*/
//然后在html中引用php页面：
/*
<img  title="点击刷新" src="./captcha.php" align="absbottom" onclick="this.src='captcha.php?'+Math.random();"></img>
*/

?>