mysql动态拼接sql语句

<?php
$host = 'localhost';
$user = 'root';
$password = 'password';
$dbname = 'testdb';

// 创建连接
$conn = new mysqli($host, $user, $password, $dbname);

if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 动态拼接 SQL 语句
$name = $_GET['name'] ?? '';
$age = $_GET['age'] ?? '';

$sql = "SELECT * FROM users";
$params = [];

if (!empty($name)) {
    $sql .= " WHERE name = ?";
    $params[] = $name;
}

if (!empty($age)) {
    if (count($params) > 0) {
        $sql .= " AND";
    } else {
        $sql .= " WHERE";
    }
    $sql .= " age = ?";
    $params[] = $age;
}

// 执行查询
$stmt = $conn->prepare($sql);
$stmt->bind_param(str_repeat('s', count($params)), ...$params);
$stmt->execute();
$result = $stmt->get_result();

// 处理结果
while ($row = $result->fetch_assoc()) {
    echo "Name: " . $row["name"] . " Age: " . $row["age"] . "<br>";
}

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