PHP生成随机验证码

验证码的生成

<?php
// 开启session
session_start();
// 生成随机验证码
$charset = '0123456789ABCDEFGHIJKLMNPQRSTUVWXYZabcvbnmasdfghjkpiuytrewq';
$randomString = '';
// 验证码长度
$length = 6; 
$charsetLength = strlen($charset) - 1;
for ($i = 0; $i < $length; $i++) {
    $randomString .= $charset[random_int(0, $charsetLength)];
}
// 保存验证码到session中
$_SESSION['captcha'] = $randomString;
// 创建验证码图片
$image = imagecreatetruecolor(120, 40);
$bgColor = imagecolorallocate($image, 255, 255, 255);
$textColor = imagecolorallocate($image, 0, 0, 0);
// 填充背景色
imagefilledrectangle($image, 0, 0, 120, 40, $bgColor);
// 在图片上绘制验证码
imagestring($image, 5, 40, 10, $randomString, $textColor);
// 发送图像头部到浏览器
header('Content-Type: image/png');
// 输出图像到浏览器
imagepng($image);
// 销毁图像资源
imagedestroy($image);
?>

验证码的调用

<div id="popup" class="popup">
    <div class="popup-inner">
      <center><h3>用户注册</h3></center>
      <span class="button-close" onclick="closePopup()">&times;</span>
      <form id="joinForm" action="sub.php" method="POST">
        <div class="form-group">
          <label for="username">账号：</label>
          <input type="text" id="username" name="username" placeholder="请输入账号" required>
        </div>
        <div class="form-group">
          <label for="userpass">密码：</label>
          <input type="pass" id="userpass" name="userpass" placeholder="请输密码" required>
        </div>
        <div class="form-group">
          <label for="captcha">验证码：<img class="ue-image" src="yzm.php"/></label>
          <input type="text" id="captcha" name="captcha" placeholder="请输入验证码" required>
        </div>
        <div class="form-group">
          <div class="button-group">
            <button type="submit">提交</button>
          </div>
        </div>
      </form>
    </div>
  </div>

验证码的验证

<?php
//开启session
session_start();
if(!empty($_POST)){
  $username = $_POST['username'];
  $userpass = $_POST['userpass'];
  $captcha = $_POST['captcha'];
  if (!preg_match('/^[A-Za-z0-9]+$/', $captcha)) {
    //判断验证码的合法性，如果验证码未按0-9和a-Z的规则输入则提示验证码不正确并返回首页。
    echo '<script>alert("验证码不正确！"); window.location.href = "index.php";</script>';
    exit;    
  }
  if($captcha!=$_SESSION['captcha']){
    //判断输入的验证码是否与生成的验证码一致，如果不一致则提示验证码不正确并返回首页。
    echo '<script>alert("验证码不正确！"); window.location.href = "index.php";</script>';
    exit;      
  }else{
  //如果验证码正确，则继续执行代码
  
  }
}
?>