mysql 不显示字段名

SELECT id, name, email FROM users;

$result = mysqli_query($conn, "SELECT id, name, email FROM users");
while ($row = mysqli_fetch_assoc($result)) {
    echo "ID: " . $row["id"] . " - Name: " . $row["name"] . " - Email: " . $row["email"] . "<br>";
}

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 查询语句
$sql = "SELECT id, name, email FROM users";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // 输出字段名
    $field_names = $result->fetch_fields();
    foreach ($field_names as $field) {
        echo $field->name . "\t";
    }
    echo "\n";

    // 输出数据
    while($row = $result->fetch_assoc()) {
        echo $row["id"] . "\t" . $row["name"] . "\t" . $row["email"] . "\n";
    }
} else {
    echo "0 结果";
}
$conn->close();
?>