如何在php中使用if条件在while循环中插入数据？

<?php
// 连接数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

$conn = new mysqli($servername, $username, $password, $dbname);

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

// 查询年龄小于18岁的用户
$sql = "SELECT id, name, age FROM users WHERE age < 18";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
        // 检查是否已经存在记录
        $check_sql = "SELECT id FROM user_logs WHERE user_id = " . $row["id"];
        $check_result = $conn->query($check_sql);

        if ($check_result->num_rows == 0) {
            // 如果不存在记录，则插入新记录
            $insert_sql = "INSERT INTO user_logs (user_id, log_message) VALUES (" . $row["id"] . ", 'Age less than 18')";
            if ($conn->query($insert_sql) === TRUE) {
                echo "新记录插入成功 for user: " . $row["name"] . "<br>";
            } else {
                echo "Error: " . $insert_sql . "<br>" . $conn->error;
            }
        }
    }
} else {
    echo "0 结果";
}

$conn->close();
?>