如何使用 PHP 函数与数据库交互？

$servername = "localhost";

$username = "username";

$password = "password";

$dbname = "database";

// 创建连接

$conn = new Mysqli($servername, $username, $password, $dbname);

// 检查连接是否成功

if ($conn->connect_error) {

    die("连接失败: " . $conn->connect_error);

}

$sql = "SELECT * FROM users";

$result = $conn->query($sql);

// 检查查询是否成功

if (!$result) {

    die("查询失败: " . $conn->error);

}

while ($row = $result->fetch_assoc()) {

    echo $row["name"] . "<br>";

}

$sql = "INSERT INTO users (name) VALUES ('John Doe')";

if ($conn->query($sql) === TRUE) {

    echo "记录已成功插入";

} else {

    echo "插入记录失败: " . $conn->error;

}

$sql = "UPDATE users SET name='John Smith' Where id=1";

if ($conn->query($sql) === TRUE) {

    echo "记录已成功更新";

} else {

    echo "更新记录失败: " . $conn->error;

}

$sql = "DELETE FROM users WHERE id=1";

if ($conn->query($sql) === TRUE) {

    echo "记录已成功删除";

} else {

    echo "删除记录失败: " . $conn->error;

}

$conn->close();