Its showing me a syntax error, please guide [duplicate]

Error image

session_start();
if (!isset($_SESSION['unique_id'])) {
    header("location: login.php");
}
?>

<?php include_once "header.php"; ?>
<body>
    <div class="wrapper">
        <section class="chat-area">
            <header>
                <?php
                include_once "php/config.php";
                $user_id = mysqli_real_escape_string($conn, $_GET['user_id']);
                $sql = mysqli_query($conn, "SELECT * FROM users WHERE unique_id = {user_id}");
                if (mysqli_num_rows($sql) > 0) {
                    $row = mysqli_fetch_assoc($sql);
                }
                ?>
                <a href="users.php" class="back-icon"><i class="fas fa-arrow-left"></i></a>
                <img src="php/images/<?php echo $row['img'] ?>" alt="">
                <div class="details">
                    <span><?php echo $row['fname'] . " " . $row['lname'] ?></span>
                    <p><?php echo $row['status'] ?></p>
                </div>
            </header>
            <div class="chat-box">
                <div class="chat outgoing">
                    <div class="details">
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</p>
                    </div>
                </div>
                <div class="chat incoming">
                    <img src="img2.png" alt="">
                    <div class="details">
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</p>
                    </div>
                </div>
                <div class="chat outgoing">
                    <div class="details">
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</p>
                    </div>
                </div>
                <div class="chat incoming">
                    <img src="img2.png" alt="">
                    <div class="details">
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</p>
                    </div>
                </div>
                <div class="chat outgoing">
                    <div class="details">
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</p>
                    </div>
                </div>
                <div class="chat incoming">
                    <img src="img2.png" alt="">
                    <div class="details">
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</p>
                    </div>
                </div>
                <div class="chat outgoing">
                    <div class="details">
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</p>
                    </div>
                </div>
                <div class="chat incoming">
                    <img src="img2.png" alt="">
                    <div class="details">
                        <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit.</p>
                    </div>
                </div>
            </div>
            <form action="#" class="typing-area">
                <input type="text" placeholder="Type a Sandesh...">
                <button><i class="fab fa-telegram-plane"></i></button>
            </form>
        </section>
    </div>

</body>
</html>

I am making a real-time chat app using this video as reference-https://www.youtube.com/watch?v=VnvzxGWiK54. In the chat.php part I am getting an error in saying : Uncaught mysqli_sql_exception: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ‘}’ at line 1 in C:xampphtdocsSandesha codingnepalchat.php:16 Stack trace: #0 C:xampphtdocsSandesha codingnepalchat.php(16): mysqli_query(Object(mysqli), ‘SELECT * FROM u…’) #1 {main} thrown in

Plez guide what to do.