如何用 php实现验证码

php实现验证码的方法：首先创建绘制验证码类，代码如“class Captcha {...}”；然后绘制图片页面；接着设置表单页面；最后创建好验证页面即可。

本文操作环境：Windows7系统、PHP7.1版，DELL G3电脑

PHP 实现验证码

绘制验证码类

<?php
class Captcha {
    const CODE_LENGTH = 4;  // 验证码长度固定为 4，可以根据实际需要修改
    const LINE_COUNT = 4;   // 干扰线个数
    const DOT_COUNT = 200;  // 干扰点个数
    // 验证码备选字符
    static $CANDIDATES = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    public function __construct($width, $height) {
   $this->width = $width;
   $this->height = $height;
   // 创建图像对象
   $this->image = imagecreatetruecolor($width, $height);
   // 创建验证码
   $this->generateCaptchaCode();
    }
    public function __destruct() {
   // 销毁图像对象
   imagedestroy($this->image);
    }
    public function paint() {
   // 绘制背景
   $this->paintBackground();
   // 绘制验证码
   $this->paintText();
   // 绘制干扰
   $this->paintDirty();
    }
    public function output() {
   // 设置头部为PNG图片
   header('Content-Type: image/png');
   // 输出到浏览器
   imagepng($this->image);
    }
    public function code() {
   return $this->code;
    }
    private function paintBackground() {
   // 背景颜色设置为白色
   $color = imagecolorallocate($this->image, 255, 255, 255);
   // 填充背景
   imagefill($this->image, 0, 0, $color);
    }
    private function paintText() {
   // 遍历验证码，一个字符一个字符地绘制
   for ($i = 0; $i < strlen($this->code); ++$i) {
  $fontsize = 6;
  $color = imagecolorallocate($this->image, rand(0,50), rand(0,50), rand(0,50));
  $x = ($i * 100 / self::CODE_LENGTH) + rand(5, 10);
  $y = rand(5, 10);
  imagestring($this->image, $fontsize, $x, $y, $this->code[$i], $color);
   }
    }
    private function paintDirty() {
   // 绘制点
   for ($i = 0; $i < self::DOT_COUNT; ++$i) {
  // 点的颜色
  $pointcolor = imagecolorallocate($this->image, rand(100,200), rand(100,200), rand(100,200));    
  // 画点
  imagesetpixel($this->image, rand(1,99), rand(1,29), $pointcolor);
   }
   // 绘制线条
   for ($i = 0; $i < self::LINE_COUNT; $i++) {
  // 线的颜色
  $linecolor = imagecolorallocate($this->image, rand(100,200), rand(100,200), rand(100,200));
  // 画线
  imageline($this->image, rand(1,$this->width-1), rand(1,29), rand(1,99), rand(1,29), $linecolor);
   }
    }
    private function generateCaptchaCode() {
   // 从备选字符串中随机选取字符
   for ($i = 0; $i < self::CODE_LENGTH; ++$i) {
  $len = strlen(self::$CANDIDATES);
  $pos = rand(0, $len - 1);
  $ch = self::$CANDIDATES[$pos];
  $this->code .= $ch;
   }
    }
    private $image = NULL;  // 图像对象
    private $code = "";// 验证码
    private $width = 0;// 图像长度
    private $height = 0;    // 图像宽度
}
?>

绘制图片页面

<?php
session_start();  // 开启 Session，必须是第一句
require_once "./Captcha.php";
$captcha = new Captcha(100, 30);  // 创建对象
$_SESSION['captcha'] = $captcha->code();  // 将验证码存入Session
$captcha->paint();  // 绘制
$captcha->output();  // 输出
?>

推荐学习：《PHP视频教程》

表单页面

<?php
session_start();  // 开启Session，必须是第一句
?>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>提交页面</title>
    <script>
   function validate_form(form) {
  with (form) {
 if (captcha.value == null || captcha.value == "") {
alert("验证码不能为空！");
return false;
 }
  }
  return true;
   }
    </script>
</head>
<body>
    <form method="post" action="./validate.php" onsubmit="return validate_form(this)">
  验证码：<input type="text" name="captcha" value="" size=10>
  <img title="点击刷新" id="captchaImg" border="1" src="./captchaImage.php"
 onclick="this.src='./captchaImage.php?r=' + Math.random();"></img><br>
  <input type="submit"/>
    </form>
</body>
</html>

验证页面

<?php
session_start();  // 开启Session，必须是第一句
?>
<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>验证页面</title>
</head>
<body>
    <?php
    if (isset($_POST['captcha']) && strcasecmp($_POST['captcha'], $_SESSION['captcha']) == 0) {
   echo "Succeeded!";
    } else {
   ec`
o "Failed!";
    }
    ?>
</body>
</html>

以上就是如何用 php实现验证码的详细内容！

查看更多关于如何用 php实现验证码的详细内容...

声明：本文来自网络，不代表【好得很程序员自学网】立场，转载请注明出处：http://haodehen.cn/did38637

更新时间：2022-09-24 阅读：40次