mysql中动态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SQL示例
$sql = "SELECT * FROM users WHERE 1=1";
$params = [];

if (isset($_GET['name'])) {
    $sql .= " AND name = ?";
    $params[] = $_GET['name'];
}

if (isset($_GET['age'])) {
    $sql .= " AND age = ?";
    $params[] = $_GET['age'];
}

$stmt = $conn->prepare($sql);
$stmt->bind_param(str_repeat("s", count($params)), ...$params);

$stmt->execute();
$result = $stmt->get_result();

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

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