PHP怎样连接MySQL数据库？

方法一：使用 mysqli 扩展

mysqli 是 MySQL 的改进版扩展，提供了面向对象和过程化的接口。

面向对象风格

<?php

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

// 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);
}

echo "连接成功";

// 执行查询示例
$sql = "SELECT id, name FROM your_table";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // 输出数据
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
    }
} else {
    echo "0 结果";
}

// 关闭连接
$conn->close();

?>

过程化风格

<?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
if (!$conn) {
    die("连接失败: " . mysqli_connect_error());
}

echo "连接成功";

// 执行查询示例
$sql = "SELECT id, name FROM your_table";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // 输出数据
    while($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);

?>

方法二：使用 PDO 扩展

PDO 提供了一个统一的接口来访问多种数据库，支持参数化查询，能有效防止SQL注入。

<?php

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

try {
    // 创建连接
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    // 设置 PDO 错误模式为异常
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    echo "连接成功";

    // 执行查询示例
    $sql = "SELECT id, name FROM your_table";
    $stmt = $conn->prepare($sql);
    $stmt->execute();

    // 设置结果为关联数组
    $result = $stmt->setFetchMode(PDO::FETCH_ASSOC);
    foreach ($stmt->fetchAll() as $row) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. "<br>";
    }
} catch(PDOException $e) {
    echo "连接失败: " . $e->getMessage();
}

// 连接会在脚本结束时自动关闭，但你可以显式关闭
$conn = null;

?>

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