PHP将SQL表更新为登录用户

Question

I'm trying to get a logged in user's input from a text box to be inserted into a column on their row. Right now I am able to insert data into my database but it comes up as a new record. I'm struggling to find a way to point it to the specific logged in user so it adds to that row rather than creating a new record.

form code in payment.php :

<form class="test" action="payment.php" method="post" autocomplete="off">
    <input type="text" required class="text" name='bitaddress' placeholder="Public Key...">
    <input class="wow shake" data-wow-delay="0.3s" type="submit" value="Accept" name="accept" />
</form>

PHP code in payment.php :

<?php 
if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    if (isset($_POST['accept'])) { 
        require 'paymentProccess.php';    
    }
}
?>

lastly my code inside paymentProccess.php :

<?php
require 'db.php';

$bitaddress = $mysqli->escape_string($_POST['bitaddress']);

$user_name = $_SESSION['user_name'];
$email = $_SESSION['email'];
$active = $_SESSION['active'];
$paid = $_SESSION['paid'];

$sql = "INSERT INTO users (bitaddress) " . "VALUES ('$bitaddress')";
if ( $mysqli->query($sql) ){

}
?>

Answer 1

Thanks for the comments of help. After 3-4 hours I ended up working it out if anyone else has this issue.

firstly I got the "id" for the user which is my primary key.

$id = $_SESSION['id'];

then on my paymentProccess.php page I used this:

<?php
require 'db.php';

$bitaddress = $mysqli->escape_string($_POST['bitaddress']);

$user_name = $_SESSION['user_name'];
$email = $_SESSION['email'];
$active = $_SESSION['active'];
$paid = $_SESSION['paid'];
$id = $_SESSION['id'];

$sql = "UPDATE users SET bitaddress = '$bitaddress' WHERE id = '$id'";

if ( $mysqli->query($sql) ){

}
?>

note: I'm not sure if this is the most efficient way of doing it. It could have security flaws etc. But when i refreshed phpMyAdmin I had a massive amount of stress relieved.