PHP如何连接MySQL数据库 PHP数据库操作的基础教程

<?php
$dsn = 'mysql:host=localhost;dbname=your_database;charset=utf8mb4';
$username = 'your_username';
$password = 'your_password';

try {
    $pdo = new PDO($dsn, $username, $password);
    // 设置错误模式为抛出异常，这样可以更好地捕获错误
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC); // 默认返回关联数组

    echo "数据库连接成功！<br>";

    // 示例：执行一个简单的查询
    $stmt = $pdo->query("SELECT id, name FROM users LIMIT 5");
    while ($row = $stmt->fetch()) {
        echo "ID: " . htmlspecialchars($row['id']) . ", Name: " . htmlspecialchars($row['name']) . "<br>";
    }

} catch (PDOException $e) {
    // 实际项目中，这里不应该直接输出错误信息，而是记录到日志文件
    echo "数据库连接失败或查询出错: " . $e->getMessage();
    // 生产环境中，只显示一个友好的错误页面
    // error_log("数据库错误: " . $e->getMessage());
}
?>

<?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) {
    // 同样，生产环境不直接暴露错误
    die("连接失败: " . $conn->connect_error);
}
echo "数据库连接成功！<br>";

// 设置字符集
$conn->set_charset("utf8mb4");

// 示例：执行一个简单的查询
$sql = "SELECT id, name FROM users LIMIT 5";
$result = $conn->query($sql);

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

// 关闭连接
$conn->close();
?>

host

username

password

database name

systemctl status mysql

service mysql status

mysql.user

GRANT

GRANT ALL PRIVILEGES ON your_database.* TO 'your_username'@'localhost' IDENTIFIED BY 'your_password';

INSERT INTO

// PDO 插入示例
$stmt = $pdo->prepare("INSERT INTO users (name, email) VALUES (:name, :email)");
$stmt->bindParam(':name', $name);
$stmt->bindParam(':email', $email);
$name = '张三';
$email = 'zhangsan@example.com';
$stmt->execute();
echo "新记录插入成功！";

// MySQLi 插入示例 (面向对象)
$stmt = $conn->prepare("INSERT INTO users (name, email) VALUES (?, ?)");
$stmt->bind_param("ss", $name, $email); // "ss" 表示两个字符串参数
$name = '李四';
$email = 'lisi@example.com';
$stmt->execute();
echo "新记录插入成功！";
$stmt->close();

SELECT

// PDO 查询示例
$stmt = $pdo->prepare("SELECT id, name, email FROM users WHERE id > :min_id");
$minId = 10;
$stmt->bindParam(':min_id', $minId, PDO::PARAM_INT);
$stmt->execute();
$users = $stmt->fetchAll(); // 获取所有结果
foreach ($users as $user) {
    echo "ID: " . htmlspecialchars($user['id']) . ", Name: " . htmlspecialchars($user['name']) . "<br>";
}

// MySQLi 查询示例 (面向对象)
$stmt = $conn->prepare("SELECT id, name, email FROM users WHERE id > ?");
$stmt->bind_param("i", $minId); // "i" 表示整数参数
$minId = 10;
$stmt->execute();
$result = $stmt->get_result(); // 获取结果集
while ($row = $result->fetch_assoc()) {
    echo "ID: " . htmlspecialchars($row['id']) . ", Name: " . htmlspecialchars($row['name']) . "<br>";
}
$stmt->close();

UPDATE

// PDO 更新示例
$stmt = $pdo->prepare("UPDATE users SET email = :new_email WHERE id = :user_id");
$newEmail = 'new_email@example.com';
$userId = 1;
$stmt->bindParam(':new_email', $newEmail);
$stmt->bindParam(':user_id', $userId, PDO::PARAM_INT);
$stmt->execute();
echo "记录更新成功！";

DELETE FROM

// PDO 删除示例
$stmt = $pdo->prepare("DELETE FROM users WHERE id = :user_id");
$userIdToDelete = 2;
$stmt->bindParam(':user_id', $userIdToDelete, PDO::PARAM_INT);
$stmt->execute();
echo "记录删除成功！";