当我将javascript变量存储在mysql中时，如何将其链接到当前用户的ID？

Question

Let's say there is a site that has a button that uses javascript to increase the value of the javascript variable "javascriptx" by +1 each time it is clicked. UserA (id=1 on the MySql table) logs in to the website and presses the button 3 times, so javascriptx = 2.

The next time UserA logs in, I want javascriptx to still equal 2 (assuming the button hasn't been pressed any more times), so I need to convert that javascript variable to a php variable and send it to MySql. As far as I understand, this is the correct way to do that:

Add the following to the javascript code:

var xhr = new XMLHttpRequest();
xhr.open("get","/path/to/php/page.php?phpx=javascriptx");
xhr.send();

Now, the php variable "phpx" has the same value as the javascript variable "javascriptx"

Then, that php variable needs to be sent to the MySql table, so the following is added to the php code:

($_GET['phpx'])

From here, I get lost. Where does phpx get stored in the MySql table? More specifically, how does it know to put this in the same row as user with id=1?

Answer 1

You should connect to the MySQL database using something like mysqli :

$database = new mysqli(db_host, db_username, db_pass, db_name);

Then you can make queries to your database with prepared statements to read/write data. In this rough example, the data will return a JSON response to your web application or wherever you make the request from:

//set user id from post variable
$uid = $_POST['uid'];

//store sql query as string
$sql = "SELECT phpx FROM users WHERE uid=?";

//initiate new prepared statement
$stmt = $database->stmt_init();
$stmt->prepare($sql);

//pass uid var to statement
$stmt->bind_param('s', $uid);

//store result as var
$stmt->bind_result($phpx);

$stmt->execute();

//catch errors
if ($stmt->errno) {
    die("error: " . $stmt->error);
} else {

//store result and send as response
    $stmt->store_result();
    if($stmt->num_rows){
        while($stmt->fetch()){
            $phpx_packet[] = array(
                "uid" => $uid,
                "phpx" => $phpx
            );
        }
        echo json_encode($phpx_packet);
    }
}

//close statement
$stmt->close();