如何用php和MySQL写代码

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database_name";

// 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);
}

// SQL 语句创建表
$sql = "CREATE TABLE users (
  id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  name VARCHAR(30) NOT NULL,
  email VARCHAR(50) NOT NULL
)";

// 执行 SQL 语句
$conn->query($sql);

// SQL 语句插入数据
$sql = "INSERT INTO users (name, email) VALUES ('John', 'john@example.com')";

// 执行 SQL 语句
$conn->query($sql);

// SQL 语句查询数据
$sql = "SELECT * FROM users";

// 执行 SQL 语句
$result = $conn->query($sql);

// 遍历结果
while($row = $result->fetch_assoc()) {
  echo $row["id"] . " " . $row["name"] . " " . $row["email"] . "<br>";
}

// SQL 语句更新数据
$sql = "UPDATE users SET name='Jane' WHERE id=1";

// 执行 SQL 语句
$conn->query($sql);

// SQL 语句删除数据
$sql = "DELETE FROM users WHERE id=1";

// 执行 SQL 语句
$conn->query($sql);

// 关闭连接
$conn->close();