php中mysql怎么连接数据库

<?php
$servername = "localhost";
$username = "your_username";
$password = "your_password";
$dbname = "your_database";

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

// 检查连接是否成功
if (!$conn) {
    die("连接失败: " . mysqli_connect_error());
}

// 执行数据库操作
$sql = "SELECT * FROM your_table";
$result = mysqli_query($conn, $sql);

// 处理查询结果
if (mysqli_num_rows($result) > 0) {
    while($row = mysqli_fetch_assoc($result)) {
        echo "ID: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
    }
} else {
    echo "0 结果";
}

// 关闭连接
mysqli_close($conn);
?>

<?php
$servername = "localhost";
$username = "your_username";
$password = "your_password";
$dbname = "your_database";

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname;charset=utf8", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "连接成功";
    
    // 执行数据库操作
    $sql = "SELECT * FROM your_table";
    $stmt = $conn->prepare($sql);
    $stmt->execute();

    // 处理查询结果
    $result = $stmt->fetchAll(PDO::FETCH_ASSOC);
    foreach ($result as $row) {
        echo "ID: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
    }
    
    // 关闭连接
    $conn = null;
} catch(PDOException $e) {
    echo "连接失败: " . $e->getMessage();
}
?>