How to send PHP post request on canvas click

I am trying to send post request to my SQL database via PHP when user clicks on canvas.
I am stuck on this for a few days and tried a lot of solutions from internet but none of the worked. There’s not much code that I have, but here’s my post request

$sendData = "send me";
$conn = new mysqli('localhost','root','','database');
    if($conn->connect_error){
        echo "$conn->connect_error";
        die("Connection Failed : ". $conn->connect_error);
    } else {
        $stmt = $conn->prepare("INSERT INTO table(data) values(?)");
        $stmt->bind_param("s", $sendData);
        $execval = $stmt->execute();
        echo $execval;
        echo "Nice";
        $stmt->close();
        $conn->close();
    }

I don’t want to do post request in JS (inside <script>) because as I am informed users can see code inside <script> and can’t see it inside <?php ?>