How Can I get Id value from the incoming url? - php

Question

When users comming this link www.sitename.com/index.php?userid=1
But user dont need to login.
I want to do change some value for the ID =1 user at the database. How can I change value. When the user just come this url address ?
This is my index.php code: (that include some other codes about qr code)
<?php
require "header.php";
require_once 'phpqrcode/qrlib.php';
$path='img/';
$file = $path.uniqid().".png";
?>
<?php
echo 'Current PHP version: ' . phpversion();
?>
<main>
<div class="wrapper-main">
<section class="section-default">
<?php
if (!isset($_SESSION['userID'])) {
echo '<p class="login-status">You are logged out!</p>';
}
else if (isset($_SESSION['userID'])) {
$text="http://sitename.com/project/userid{$_SESSION["userID"]}";
echo '<p class="login-status">You are logged in!</p>';
QRcode::png($text,$file,'L',10,2);
echo "<center><img src='".$file."'></center> " ;
}
?>
</section>
</div>
</main>
<?php
require "footer.php";
?>
EDIT 1
When I try this I failed where is my fault ?
<?php
if(!empty($_GET['user_idx'])){
$user_idx=$_GET['user_idx'];
require_once 'dbh.inc.php';
$sql = "UPDATE users SET balance=balance-5 WHERE user_idx='$user_idx';";
mysqli_query($conn,$sql);
}
In the dbh.inc.php
$servername ="127.0.0.1";
$dBUsername="xx";
$dBPassword="xx";
$dBName="xx";
$conn= mysqli_connect($servername,$dBUsername,$dBPassword,$dBName);
if(!$conn){
die("Connection failed:".mysqli_connect_error());
}

Answer 1

Data being fetched from the URL directly may be accessed or retrieved via the GET method
For your URL www.sitename.com/index.php?userid=1, you may access the userid=1 part by using the code $_GET['userid'] // which will result into "1"
Now, if you want to change it, you may create a link then pass a variable or new value to it:
In your case:
$text="http://sitename.com/project?userid{$_SESSION["userID"]}";
//we will treat the "userid" as a variable now
//so for you to fetch it, use:
//$_GET['userid']