PHP操作MySQL数据库--查询数据并输出到web页面

数据库中有数据表hacker，现在我们要将hacker表中的数据查询出来并在页面上显示，代码如下：

<?php
    // 连接数据库
    $mysqli = mysqli_connect("localhost","root","123",student);     //mysqli_close($con);
    $mysqli ? print yes!<br>:print "no!<br>";

    $sql = $mysqli -> query(use student);
    $sql = $mysqli -> query(set name utf8);

    // 创建数据表
    $sql = $mysqli -> query("create table hacker(
        id char(6) not null,
        name char(8) not null,
        chinese float not null,
        math float not null,
        english float not null
    )");
    if($sql == true){
          
   
        echo 成功创建hacker表！<br>;
    }else{
          
   
        echo 创建hacker表失败！.$mysqli->error.<br>;
    }

    // 添加数据——hacker
    // $sql  = "insert into hacker values(1,张三,10,20,30);"; 
    // $sql  .= "insert into hacker values(2,李四,66,77,88);"; 
    // $sql .= "insert into hacker values(3,王二,55,44,33);"; 
    // $sql .= "insert into hacker values(4,麻子,22,55,77)"; 
    // $rows = $mysqli->affected_rows;
    // if($rows == 3){
          
   
    //     echo "添加数据成功。<br>";
    // }else{
          
   
    //     echo 添加失败。.$mysqli->error."<br>";
    // }

    $sql = $mysqli -> query("insert into hacker
        values(2,李四,66,77,88)
    ");
    $rows = $mysqli->affected_rows;
    if($rows == 1){
          
   
        echo "添加数据成功。<br>";
    }else{
          
   
        echo 添加失败。.$mysqli->error."<br>";
    }
    $sql = $mysqli -> query("insert into hacker
        values(3,王二,55,44,33)
    ");
    $rows = $mysqli->affected_rows;
    if($rows == 1){
          
   
        echo "添加数据成功。<br>";
    }else{
          
   
        echo 添加失败。.$mysqli->error."<br>";
    }
    $sql = $mysqli -> query("insert into hacker
        values(4,麻子,22,55,77)
    ");
    $rows = $mysqli->affected_rows;
    if($rows == 1){
          
   
        echo "添加数据成功。<br>";
    }else{
          
   
        echo 添加失败。.$mysqli->error."<br>";
    }

    // 数据查询
    $sql = $mysqli->query("select * from hacker");
    if($sql){
          
   
        // echo 有数据！<br>;
        $rows = $sql->num_rows;
        echo 查询结果共有.$rows.条记录<br>;
        echo "<table>
                <tr>
                    <th>序号</th>
                    <th>姓名</th>
                    <th>语文</th>
                    <th>数学</th>
                    <th>英语</th>
                <tr>
        ";

        if($rows){
          
   
            while($row = $sql->fetch_assoc()){
          
   
                // echo id = .$row[id].<br>name = .$row[name].<br>chinese = .$row[chinese].<br>math = .$row[math].<br>english = .$row[english].<br>;
                echo "<tr>
                            <td>".$row[id]."</td>
                            <td>".$row[name]."</td>
                            <td>".$row[chinese]."</td>
                            <td>".$row[math]."</td>
                            <td>".$row[english]."</td>
                    </tr>
                ";
            }
            echo "</table>";
        }else{
          
   
            echo 没有您要找的数据。<br>;
        }
    }else{
          
   
        echo MySQL语句有误。<br>.$mysqli->error.<br>;
    }

?>