php带参数查询mysql

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database_name";

try {
    // 创建PDO连接
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // 准备SQL语句
    $stmt = $conn->prepare("SELECT * FROM users WHERE username = :username AND password = :password");

    // 绑定参数
    $stmt->bindParam(':username', $username);
    $stmt->bindParam(':password', $password);

    // 设置参数值
    $username = "admin";
    $password = "password";

    // 执行查询
    $stmt->execute();

    // 获取结果
    $result = $stmt->fetchAll(PDO::FETCH_ASSOC);

    // 输出结果
    print_r($result);
} catch (PDOException $e) {
    echo "Error: " . $e->getMessage();
}

// 关闭连接
$conn = null;
?>

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database_name";

// 创建MySQLi连接
$conn = new mysqli($servername, $username, $password, $dbname);

if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
}

// 准备SQL语句
$stmt = $conn->prepare("SELECT * FROM users WHERE username = ? AND password = ?");

// 绑定参数
$stmt->bind_param("ss", $username, $password);

// 设置参数值
$username = "admin";
$password = "password";

// 执行查询
$stmt->execute();

// 获取结果
$result = $stmt->get_result();

// 输出结果
while ($row = $result->fetch_assoc()) {
    print_r($row);
}

// 关闭连接
$stmt->close();
$conn->close();
?>