php - SQL error inserting into table

I keep getting this error in my php. It worked fine when I hard set the values but doesn't seem to work with variables.

Error: INSERT INTO ContactUS (name, email, subscribed) VALUES (TEST, my@email.com, 1)
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'Anis, my@email.com, 1)' at line 1

// Create connection
            $conn = new mysqli($servername, $username, $password, $dbname);
            // Check connection
            if ($conn->connect_error) {

                die("Connection failed: " . $conn->connect_error);
            } 

            $sql = "INSERT INTO ContactUS (name, email, subscribed) VALUES ($name, $email, $subscribed)";

            if ($conn->query($sql) === TRUE) {
                echo "New record created successfully";
            } else {
                echo "Error: " . $sql . "
" . $conn->error;
            }

Answer

Values should be quoted:

$sql = "INSERT INTO ContactUS (name, email, subscribed) VALUES ('$name', '$email', '$subscribed')";

Perhaps it's better to use prepared statements as this is done automatically for you and you won't be vulnerable to SQL injections.