Update PHP query werkt niet

<?php
error_reporting(E_ALL); 
ini_set('display_errors', 'On');
?>
<?php
require ('includes/config.inc.php'); 
include ('includes/header.php');
?>
<?php
if (!isset($_SESSION['user_id'])) {
	header("Location: login.php");
	exit(); // Quit the script.
	} ?>
<!--de content van elk nieuwe pagina moet in deze sectie beginnen-->
<?php
if (isset($_GET['id']) && !empty($_GET['id']) && is_numeric($_GET['id'])){
		// Need the database connection:
		require(MYSQL);
		// Define the query.
		$query = "SELECT
							medicines.id,
							medicines.medicinename,
							medicines.genericname,
							medicines.quantity,
							medicines.expiredate,
							medicines.sellingprice,
							medicines.purchaseprice,
							medicinescompany.companyname,
							medicinescountry.countryname,
							medicinestype.medicinetypename,
							suppliers.suppliername 
				FROM medicines
							LEFT JOIN users ON users.user_id = medicines.userid
							LEFT JOIN medicines_medicinescompany ON medicines_medicinescompany.medicine_id=medicines.id
							LEFT JOIN medicinescompany ON medicines_medicinescompany.medicinecompany_id=medicinescompany.id
							LEFT JOIN medicines_medicinescountry ON medicines_medicinescountry.medicine_id=medicines.id
							LEFT JOIN medicinescountry ON medicines_medicinescountry.medicinecountry_id=medicinescountry.id
							LEFT JOIN medicines_suppliers ON medicines_suppliers.medicine_id=medicines.id
							LEFT JOIN suppliers ON medicines_suppliers.supplier_id=suppliers.id
							LEFT JOIN medicines_medicinestype ON medicines_medicinestype.medicine_id=medicines.id
							LEFT JOIN medicinestype ON medicines_medicinestype.medicinetype_id=medicinestype.id
				where 
							medicines.id='". mysqli_real_escape_string($dbc, $_GET['id'])."' AND users.user_id = '{$_SESSION['user_id']}'";
        if ($result = mysqli_query($dbc, $query)) { // Run the query.
		$row = mysqli_fetch_array($result);// Retrieve the information.
					?>
		<form action="med_expire.php" method="post">
						<table>
								<caption>Expire Insight Form</caption>
								<input type="hidden" name="id" value="<?php echo htmlentities($row['id']);?>">
							
							<tr>
								<td><label for="medicinename"><b>Medicine Name:</b></label></td>
								<td><input type="text" name="medicinename" id="medicinename" value="<?php echo htmlentities($row['medicinename']);?>" readonly/></td>
							</tr>
							<tr>
								<td><label for="genericname"><b>Generic Name:</b></label></td>
								<td><input type="text" name="genericname" id="genericname" value="<?php echo htmlentities($row['genericname']); ?>" readonly/></td>
							</tr>
							<tr>
								<td><label for="expiredate"><b>ExpireDate:</b></label></td>
								<td><input type="text" name="expiredate" id="expiredate" value="<?php echo htmlentities($row['expiredate']); ?>" readonly/></td>
							</tr>
							<tr>
								<td><label for="quantity"><b>Quantity:</b></label></td>
								<td><input type="text" name="quantity" id="quantity" value="<?php echo htmlentities($row['quantity']); ?>" readonly/></td>
							</tr>
							<tr>
								<td><label for="sellingprice"><b>SellingPrice:</b></label></td>
								<td><input type="text" name="sellingprice" id="sellingprice" value="<?php echo htmlentities($row['sellingprice']); ?>" readonly/></td>
							</tr>
							<tr>
								<td><label for="purchaseprice"><b>PurchasePrice:</b></label></td>
								<td><input type="text" name="purchaseprice" id="purchaseprice" value="<?php echo htmlentities($row['purchaseprice']); ?>" readonly/></td>
							</tr>
							<tr>
								<td><label for="companyname"><b>CompanyName:</b></label></td>
								<td><input type="text" name="companyname" id="companyname" value="<?php echo htmlentities($row['companyname']); ?>" readonly/></td>
							</tr>
							<tr>
								<td><label for="countryname"><b>CompanyName:</b></label></td>
								<td><input type="text" name="countryname" id="countryname" value="<?php echo htmlentities($row['countryname']); ?>" readonly/></td>
							</tr>
							<tr>
								<td><label for="medicinetypename"><b>MedicineTypeName</b></label></td>
								<td><input type="text" name="medicinetypename" id="medicinetypename" value="<?php echo htmlentities($row['medicinetypename']); ?>" readonly/></td>
							</tr>
							<tr>
								<td><label for="suppliername"><b>SupplierName:</b></label></td>
								<td><input type="text" name="suppliername" id="suppliername" value="<?php echo htmlentities($row['suppliername']); ?>" readonly/></td>
							</tr>
							<tr>
								<td><input type="submit" name="submit" value="Remove from Expire View"></td>
							</tr>
						</table>
					</form>
<?php
			
			} else { // Couldn't get the information.
						echo '<p style="color: red;">Could not retrieve the medicine ID</p>';
		}
	} elseif (isset($_POST['id']) && is_numeric($_POST['id'])) { // Handle the form.
	
	$problem = FALSE;
	if (!$problem) {

		// Define the query.
		$query = "UPDATE medicines SET verwijderd = 2 WHERE id={$_POST['id']}";
		$r = mysqli_query($dbc, $query); // Execute the query.

		// Report on the result:
		if (mysqli_affected_rows($dbc) == 1) {
			print '<p>This medicine has been removed from the Expire View.</p>';
		} else {
			echo '<p style="color: red;">Could not update the entry<br></p>';
		}

	} // No problem!

} else { // No ID set.
	print '<p style="color: red;">This page has been accessed in error.</p>';
} // End of main IF.
?>
<!--ending header-->
<?php
include ('includes/footer.php');
?>