PHP实现简易用户登录系统

?php
$servername = "localhost";
$username = "formbd";
$password = "formbd";
$dbname = "form";
 
// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);
 
// 检测连接
if ($conn->connect_error) {
  die("连接失败: " . $conn->connect_error);
}

?>

!doctype html>
html lang="en">
  head>
    meta charset="UTF-8">
    title>用户注册页面/title>
  /head>
  body>
    form action="reg.php" method="post">
      p>用户名:input type="text" name="name">/p>
      p>密 码: input type="text" name="password">/p>
      p>input type="submit" name="submit" value="注册">
        a href="login.html" >input type="button" name="login" value="已有账号，返回登录">/a>
      /p>
    /form>
  /body>
/html>

?php 
  header("Content-Type: text/html; charset=utf8");

  if(!isset($_POST['submit'])){
    exit("错误执行");
  }//判断是否有submit操作

  $name=$_POST['name'];//post获取表单里的name
  $user_password=$_POST['password'];//post获取表单里的password

  include('connect.php');//链接数据库
  $q="insert into user(id,username,password) values (null,'$name','$user_password')";//向数据库插入表单传来的值的sql
  $sql = "select * from user where username = '$name'";
  
  if (($conn->query($sql))==$name) {
    echo '用户名已存在';
    $result = $conn->query($sql);
    /*echo "
          script>
              setTimeout(function(){window.location.href='reg.html';},1000);
          /script>

        ";*/
  }
  else {
  $conn->query($q);
  echo "注册成功";
  echo "
          script>
              setTimeout(function(){window.location.href='login.html';},1000);
          /script>

        ";
}
  
  $conn->close();//关闭数据库

?>

!doctype html>
html lang="en">
  head>
    meta charset="UTF-8">
    title>登陆/title>
  /head>
  body>
    form name="login" action="login.php" method="post">
        p>用户名input type=text name="name">/p>
        p>密 码input type=password name="password">/p>
        p>input type="submit" name="submit" value="登录">
          a href="reg.html" >input type="button" name="reg" value="注册">/a>
        /p>

      /form>
  /body>
/html>

?PHP
  header("Content-Type: text/html; charset=utf8");
  if(!isset($_POST["submit"])){
    exit("错误执行");
  }//检测是否有submit操作

  include('connect.php');//链接数据库
  $name = $_POST['name'];//post获得用户名表单值
  $passowrd = $_POST['password'];//post获得用户密码单值

  if ($name  $passowrd){//如果用户名和密码都不为空
       $sql = "select * from user where username = '$name' and password='$passowrd'";//检测数据库是否有对应的username和password的sql

       $result = $conn->query($sql);//执行sql
       $rows=$result->fetch_assoc();//返回一个数值
       if($rows){//0 false 1 true
          header("refresh:0;url=success.php");//如果成功跳转至success.php页面
          exit;
       }else{
        echo "用户名或密码错误";
        echo "
          script>
              setTimeout(function(){window.location.href='login.html';},1000);
          /script>

        ";//如果错误使用js 1秒后跳转到登录页面重试;
       }
      

  }else{//如果用户名或密码有空
        echo "表单填写不完整";
        echo "
           script>
              setTimeout(function(){window.location.href='login.html';},1000);
           /script>";

            //如果错误使用js 1秒后跳转到登录页面重试;
  }

  $conn->close();//关闭数据库
?>

?php 
include 'connect.php';
session_start(); //声明变量
$username = isset($_SESSION['nmae']) ? $_SESSION['name'] : "";
?>

!doctype html>
html lang="en">
  head>
    meta charset="UTF-8">
    title>登陆成功/title>
  /head>
  body>
    欢迎光临
    ?php echo $username;?>
    ?php ?>
  /body>
/html>