Database input sanitisation with PHP forms - php

Question

I sanitise the data I receive from the form in the following way:
$gender = filter_var($_POST['gender'], FILTER_SANITIZE_STRING);
$firstName = filter_var($_POST['firstName'], FILTER_SANITIZE_STRING);
$lastName = filter_var($_POST['lastName'], FILTER_SANITIZE_STRING);
$email = filter_var($_POST['email'], FILTER_SANITIZE_EMAIL);
$message = filter_var($_POST['comment'], FILTER_SANITIZE_STRING);
$address = filter_var($_POST['address'], FILTER_SANITIZE_STRING);
$numBrochures = (int) filter_var($_POST['quantity'], FILTER_SANITIZE_NUMBER_INT);
The relevant SQL queries that insert the data are as follows:
if (mysqli_query($conn, "INSERT INTO users(firstName, lastName, email, gender) VALUES('$firstName', '$lastName', '$email', '$gender')") == TRUE) {
logSuccess($file, "Adding user");
}
else {
logError($file, "Adding user", mysqli_error($conn));
}
$userId = $conn->query("SELECT `userId` FROM users WHERE `firstName` = '$firstName' AND `lastName` = '$lastName' AND `email` = '$email'")->fetch_object()->userId;
if ($userId == false) {
logError($file, "Fetching user id", mysqli_error($conn));
}
if (mysqli_query($conn, "INSERT INTO brochureOrders(userId, address, numBrochures, message) VALUES('$userId', '$address', '$numBrochures', '$message')") == TRUE) {
logSuccess($file, "Brochure Order");
$sendConfirmationEmail = true;
}
else {
logError($file, "Brochure Order", mysqli_error($conn));
}
However, in my database, I see entries like the following:
address = "vz8y8E gghwptvvzuak, [url=http://ytvsmximkjnp.com/]ytvsmximkjnp[/url], [link=http://hiabgyvsjifp.com/]hiabgyvsjifp[/link], http://tyvylndqitoy.com/"
Shouldn't the following have taken care of this?
$address = filter_var($_POST['address'], FILTER_SANITIZE_STRING);
Could someone tell me what I am doing incorrectly here?

Answer 1

Because the OP stated in the comments he wants to switch to prepared statement, I thought I'd show him an example.
Instead of something like this:
if (mysqli_query($conn, "INSERT INTO users(firstName, lastName, email, gender) VALUES('$firstName', '$lastName', '$email', '$gender')") == TRUE) {
logSuccess($file, "Adding user");
}
else {
logError($file, "Adding user", mysqli_error($conn));
}
Do something like this:
$query = "INSERT INTO users (firstName, lastName, email, gender) VALUES(?, ?, ?, ?)";
if($stmt = $mysqli->prepare($query)){
$stmt->bind_param('ssss', $firstName, $lastName, $email, $gender);
$stmt->exeucte();
$stmt->close();
}else die("Failed to prepare!");
and this
$query = "SELECT `userId` FROM users WHERE `firstName` = ? AND `lastName` = ? AND `email` = ?";
if($stmt = $mysqli->prepare($query)){
$stmt->bind_param('sss', $firstName, $lastName, $email);
$stmt->execute();
$stmt->bind_result($userId);
$stmt->fetch();
$stmt->close()
}else die("Failed to prepare!");