Is it possible to parametarize query that has a concatenation variable? - php

Question

As learning php and sql injections, I would like to parametize my queries for safe and secure website app. however, mine does not work I try to parametize my update and select my query but I didn't achieved the goal to make the program working.
The current output is throwing an error the ? is not found
As of now here is my code, am I missing something that does not work?
<?php
//connection
$connection = mysqli_connect("hostserver","username","");
$db = mysqli_select_db($connection, 'dbname');
if (isset($_POST['qrname'])) {
$qrid = $_POST['qrid'];
//Query No. 1
$qrQuery = "SELECT * FROM scratch_cards WHERE code='$qrid' ";
$qrQuery_run = mysqli_query($connection,$qrQuery);
//Query No. 2
$qrQuery2 = "UPDATE scratch_cards SET status = 'U' WHERE code='$qrid' ";
$qrQuery_run2 = mysqli_query($connection,$qrQuery2);
$qrQuery2->bind_param("s", $qrid);
$qrQuery2->execute();
while ($qrRow = mysqli_fetch_array($qrQuery_run)) {
$txtQrvalue = $qrRow['amount'];
$txtQrstatus = $qrRow['status'];
// QUERY TO UPDATE THE VALUE
// BIND AND PARAMETIZE MY QUERY
$qrQuery3 = $db->parepare("UPDATE shopusers SET ewallet = ewallet + " . (0+?) . " WHERE id = '?' ");
$qrQuery3->bind_param("ii", $txtQrvalue, $id);
$qrQuery3->execute();
//END
}

Answer 1

If I'm reading your question and code right, you can reduce this down to two queries using a JOIN instead, that way you can get rid of the SELECT statement. Use prepared statements for both.
I also specified your connection's charset to UTF-8 (which you should set for your PHP and HTML headers, and your database-tables too).
<?php
$connection = mysqli_connect("hostserver","username","");
$db = mysqli_select_db($connection, 'dbname');
$connection->set_charset("utf8");
if (isset($_POST['qrname'])) {
$qrid = $_POST['qrid'];
$sql = "UPDATE scratch_cards SET status = 'U' WHERE code=?";
$stmt = $connection->prepare($sql);
$stmt->bind_param("s", $qrid);
$stmt->execute();
$stmt->close();
$sql = "UPDATE shopusers su
INNER JOIN scratch_cards sc
ON sc.qrid = su.code
SET su.ewallet = su.ewallet + sc.amount,
sc.status = 'U'
WHERE sc.code = ?";
$stmt = $connection->prepare($sql);
$stmt->bind_param("s", $qrid);
$stmt->execute();
$stmt->close();
}

Answer 2

we have the foll syntax in PDO bind param, where i have put your update query as an example and it works perfectly fine. Try searching for named parameter binding
<?php
$user = 'root';
$pass = 'xxxx';
$DB = 'test';
$host = 'localhost';
$mysqlConnection = new \PDO('mysql:host='.$host.';dbname='.$DB, $user, $pass);
$mysqlConnection->setAttribute(\PDO::ATTR_ERRMODE, \PDO::ERRMODE_EXCEPTION);
$sql = 'update info set fname = fname + :fn where id = 1';
$stmt = $mysqlConnection->prepare($sql);
$stmt->bindValue(':fn', '100');
$stmt->execute();
echo $stmt->rowCount();
?>

Answer 3

Is this the query you wanted to run using mysqli bind params???
<?php
ini_set('display_errors', 1);
$user = 'root';
$pass = 'xxxx';
$DB = 'test';
$host = 'localhost';
$sql = 'update info set fname = fname + ? where id = 1';
$conn = new mysqli($host, $user, $pass, $DB);
$stmt = $conn->prepare($sql);
$stmt->bind_param("i", $val);
$val = 100;
$stmt->execute();
printf("%d Row inserted.\n", $stmt->affected_rows);
exit;