php - 我正在尝试将 MySQL 数据库中的数据显示到 HTML 表上，但没有注册列字段

Question

我是 PHP 编码新手，不明白哪里出了问题，我试图将 MySQL 数据库中的数据显示到 HTML 表上，但没有注册列字段，不断出现通知: undefined index :首先，注意: undefined index :最后等。如何定义我的列字段？

编辑:这里是我的数据库图片和我收到的错误代码的链接:http://imgur.com/E5uohjr http://imgur.com/BGDn9SQ

这是我的代码:

</head>

$con = mysqli_connect('localhost', 'root', '', 'form_database') or die("Can not connect: " . mysqli_error());

$result = mysqli_query($con,"SELECT first, last, phone, class FROM form_submissions");

echo "<table border=1>
<tr>
<th>First Name</th>
<th>Last Name</th>
<th>Phone Number</th>
<th>Class interested in</th>
</tr>"; 

while($row = mysqli_fetch_assoc($results)){
echo "<tr>";
echo "<td>" . $row['first'] . "</td>";
echo "<td>" . $row['last'] . "</td>";
echo "<td>" . $row['phone'] . "</td>";
echo "<td>" . $row['class'] . "</td>";
echo "</tr>";
}

echo "</table>";

mysqli_close($con);

?>
</body>

Answer 1

在显示结果之前检查是否有结果。

<?php
// Create connection
$con = mysqli_connect('localhost', 'root', '', 'form_database');
// Check connection
if (!$con) {
    die("Connection failed: " . mysqli_connect_error());
}

$sql    = "SELECT * FROM form_submissions";
$result = mysqli_query($con, $sql);

//check if you get any results
if (mysqli_num_rows($result) > 0) {
    echo "<table border=1>
        <tr>
        <th>First Name</th>
        <th>Last Name</th>
        <th>Phone Number</th>
        <th>Class interested in</th>
        </tr>";

    // output data of each row
    while ($row = mysqli_fetch_assoc($result)) {
        echo "<tr>";
        echo "<td>" . $row['first'] . "</td>";
        echo "<td>" . $row['last'] . "</td>";
        echo "<td>" . $row['phone'] . "</td>";
        echo "<td>" . $row['class'] . "</td>";
        echo "</tr>";
    }
    echo "</table>";
} else {
    echo "No results found";
}

mysqli_close($con);