在PHP中的SQL查询前添加美元符号

<?php
// 假设有一个名为$name的变量需要插入到SQL查询中
$name = "John";

// 使用PDO扩展的示例代码
$pdo = new PDO("mysql:host=localhost;dbname=mydatabase", "username", "password");
$stmt = $pdo->prepare("SELECT * FROM users WHERE name = :name");
$stmt->bindParam(':name', $name);
$stmt->execute();
$result = $stmt->fetchAll(PDO::FETCH_ASSOC);

// 使用mysqli扩展的示例代码
$mysqli = new mysqli("localhost", "username", "password", "mydatabase");
$stmt = $mysqli->prepare("SELECT * FROM users WHERE name = ?");
$stmt->bind_param("s", $name);
$stmt->execute();
$result = $stmt->get_result()->fetch_all(MYSQLI_ASSOC);

// 处理查询结果
foreach ($result as $row) {
    echo $row['name'] . "<br>";
}
?>