php数据库的连接函数

// 示例代码：使用 mysqli_connect() 连接 MySQL 数据库
$host = 'localhost';
$user = 'username';
$password = 'password';
$dbname = 'database_name';

$conn = mysqli_connect($host, $user, $password, $dbname);

if (!$conn) {
    die('连接失败: ' . mysqli_connect_error());
}
echo '连接成功';

// 示例代码：使用 PDO 连接 MySQL 数据库
$host = 'localhost';
$dbname = 'database_name';
$user = 'username';
$password = 'password';

try {
    $pdo = new PDO("mysql:host=$host;dbname=$dbname", $user, $password);
    echo '连接成功';
} catch (PDOException $e) {
    echo '连接失败: ' . $e->getMessage();
}

// 示例代码：使用 mysqli 预处理语句防止 SQL 注入
$stmt = $conn->prepare("SELECT * FROM users WHERE username = ?");
$stmt->bind_param("s", $username);

$username = $_POST['username'];
$stmt->execute();

$result = $stmt->get_result();
while ($row = $result->fetch_assoc()) {
    echo $row['username'] . '<br>';
}
$stmt->close();

// 示例代码：使用 PDO 预处理语句防止 SQL 注入
$stmt = $pdo->prepare("SELECT * FROM users WHERE username = :username");
$stmt->bindParam(':username', $username);

$username = $_POST['username'];
$stmt->execute();

$result = $stmt->fetchAll(PDO::FETCH_ASSOC);
foreach ($result as $row) {
    echo $row['username'] . '<br>';
}