mysql 动态拼接sql

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

// 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);
}

// 动态拼接 SQL 语句
$userInput = $_GET['user']; // 假设用户输入通过 GET 请求传递
$sql = "SELECT * FROM users WHERE username = '" . $userInput . "'";

$result = $conn->query($sql);

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

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

// 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);
}

// 动态拼接 SQL 语句
$userInput = $_GET['user']; // 假设用户输入通过 GET 请求传递
$stmt = $conn->prepare("SELECT * FROM users WHERE username = ?");
$stmt->bind_param("s", $userInput);

$stmt->execute();

$result = $stmt->get_result();

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

$stmt->close();
$conn->close();
?>

$stmt = $conn->prepare("SELECT * FROM users WHERE username = ?");
$stmt->bind_param("s", $userInput);