Warning: mysqli_query() expects at least 2 parameters, 1 given in /home/tdoylex1/public_html/dorkhub/index.php on line 4

大概意思是mysqli_query()至少需要2个参数，其中1个给定。

原本的代码是

  <?php
     $name = $_POST['name'];
        $password = $_POST['password'];
 try{
        $pdo = new PDO("mysql:host=localhost;dbname=php;","root","123456");
    }catch(PDOException $e){
        die("数据库连接失败".$e->getMessage());
    }
  
     $sql = "SELECT * FROM login WHERE username ='{$name}' and password='{$password}'";
    
      $rst=mysqli_query( $sql);
    $row=mysqli_fetch_assoc($rst);

 if($row){
     echo "<script> alert('登录成功!');
                        window.location='main2.php'; //跳转      
                    </script>";
 }
     
     else
     {
  
           echo "<script> alert('用户不存在或密码错误！');
                   window.history.back(); //返回上一页
                    </script>";
         }

           
                   
           
 
        ?>  

 

修改为

  <?php
     $name = $_POST['name'];
        $password = $_POST['password'];
 
    // .连接数据库
 
    // .防止中文乱码
    $con=mysqli_connect("localhost","root","123456","php");
          // .拼接sql语句，取出信息
  
     $sql = "SELECT * FROM login WHERE username ='{$name}' and password='{$password}'";
      $rst=mysqli_query( $con,$sql);
    $row=mysqli_fetch_assoc($rst);

 if($row){
     echo "<script> alert('登录成功!');
                        window.location='main2.php'; //跳转      
                    </script>";
 }
     
     else
     {
  
           echo "<script> alert('用户不存在或密码错误！');
                   window.history.back(); //返回上一页
                    </script>";
         }

           
                   
           
 
        ?>  

还有mysqli与mysql是看你的php版本，版本不一样代码也有一定的差别