php mysql唯一索引

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) NOT NULL,
    UNIQUE (username),
    UNIQUE (email)
);

<?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);
}

$username = "testuser";
$email = "testuser@example.com";

// 检查用户名和邮箱是否已经存在
$sql = "SELECT * FROM users WHERE username = ? OR email = ?";
$stmt = $conn->prepare($sql);
$stmt->bind_param("ss", $username, $email);
$stmt->execute();
$result = $stmt->get_result();

if ($result->num_rows > 0) {
    echo "用户名或邮箱已经存在";
} else {
    // 插入数据
    $sql = "INSERT INTO users (username, email) VALUES (?, ?)";
    $stmt = $conn->prepare($sql);
    $stmt->bind_param("ss", $username, $email);
    if ($stmt->execute()) {
        echo "新记录插入成功";
    } else {
        echo "Error: " . $sql . "<br>" . $conn->error;
    }
}

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