h1>用户注册/h1>
  form method="post" action="register_verify.php">
    input type="text" placeholder="用户名" name="username">br>br>
    input type="password" placeholder="密码" name="password">br>br>
    input type="password" placeholder="重复密码" name="password2">br>br>
    label>性别：
      input type="radio" name="sex" value="男" checked="checked">男
      input type="radio" name="sex" value="女">女/label>br>br>
    input type="email" placeholder="邮箱" name="email">br>br>
    button class="btn" type="submit">注册/button>
  /form>

?php
require "mysql.php";      //导入mysql.php访问数据库
$username=$_POST['username'];
$password=$_POST['password'];
$password2=$_POST['password2'];
$sex=$_POST['sex'];
$email=$_POST['email'];
if(checkEmpty($username,$password,$password2,$sex,$email)){
  if(checkpwd($password,$password2)){
    if(checkEmail($email)){
      if(insert($username,$password,$sex,$email))
        echo"注册成功";
    }
  }
}
//方法：判断是否为空
function checkEmpty($username,$password,$password2,$sex,$email){
  if($username==null||$password==null||$password2==null){
    echo 'html>head>Script Language="JavaScript">alert("用户名或密码为空");/Script>/head>/html>'       . "meta http-equiv=\"refresh\" content=\"0;url=register.html\">";
  }
  else{
    if($sex==null){
      echo 'html>head>Script Language="JavaScript">alert("性别为空");/Script>/head>/html>' .          "meta http-equiv=\"refresh\" content=\"0;url=register.html\">";
    }
    elseif($email==null){
      echo 'html>head>Script Language="JavaScript">alert("邮箱为空");/Script>/head>/html>' .          "meta http-equiv=\"refresh\" content=\"0;url=register.html\">";
    }
    else{
      return true;
    }
  }
}
//方法：检查两次密码是否相同
function checkpwd($password,$password2){
  if($password==$password2)
    return true;
  else
    echo 'html>head>Script Language="JavaScript">alert("两次密码不一致");/Script>/head>/html>' .        "meta http-equiv=\"refresh\" content=\"0;url=register.html\">";
}
//方法：邮箱格式验证
function checkEmail($email){
  $preg = '/^(\w{1,25})@(\w{1,16})(\.(\w{1,4})){1,3}$/';
  if(preg_match($preg, $email)){
    return true;
  }else{
    echo 'html>head>Script Language="JavaScript">alert("邮箱格式有误");/Script>/head>/html>' .        "meta http-equiv=\"refresh\" content=\"0;url=register.html\">";
  }
}
//方法：将数据插入数据库中
function insert($username,$password,$sex,$email){
  $conn=new Mysql();
  $sql="insert into user VALUE (null,'$username','$password','$sex','$email')";
  $result=$conn->sql($sql);
  if($result){
    return true;
  }
  else{
    echo 'html>head>Script Language="JavaScript">alert("写入数据库失败");/Script>/head>/html>' .        "meta http-equiv=\"refresh\" content=\"0;url=register.html\">";
  }
  $conn->close();
}