mysql动态执行sql语句

<?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);
}

// 动态生成 SQL 语句
$userInput = $_POST['userInput']; // 假设用户输入为 'John'
$sql = "SELECT * FROM users WHERE name = '" . $userInput . "'";

// 执行 SQL 语句
$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";
}
$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);
}

// 动态生成 SQL 语句
$userInput = $_POST['userInput']; // 假设用户输入为 'John'
$stmt = $conn->prepare("SELECT * FROM users WHERE name = ?");
$stmt->bind_param("s", $userInput); // "s" 表示参数类型为字符串

// 执行预处理语句
$stmt->execute();

// 绑定结果变量
$result = $stmt->get_result();

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";
}

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

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