php连接数据库，及数据表增删改查

$servername = "localhost";
$username = "root"; //用户名
$password = "密码";
$dname = '数据库名';//可选是否使用
// 创建连接
$conn = mysqli_connect($servername, $username, $password,$dname);
// 检测连接
if (!$conn) {
  die("连接失败: " . mysqli_connect_error());
}
echo "连接成功";
//换行
echo "<br>";

// 查询数据
 $sql = "SELECT * FROM 表名";
 $result = $conn->query($sql);
 if ($result->num_rows > 0) {
     // 输出数据
     while($row = $result->fetch_assoc()) {
         echo "id: " . $row["id"]. " - Name: " . $row["firstname"]. " " . $row["lastname"].$row["email"]. "<br>";
     }
 } else {
     echo "0 结果";
 }

//插入数据
$sql = "INSERT INTO MyGuests (属性名)
VALUES ('属性值')";
if ($conn->query($sql) === TRUE) {
    echo "新记录插入成功";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}
//多条插入数据
$sql = "INSERT INTO cs_asd (firstname,lastname)  VALUES ('刘某','小刘');";//注意加;
$sql .= "INSERT INTO cs_asd (firstname,lastname)  VALUES ('王某','小王')";
if (mysqli_multi_query($conn, $sql)){
  echo "新记录插入成功";
} else {
  echo "Error: " . $sql . "<br>" . $conn->error;
};