php if condition not evaluating as expected - php

Question

I have this script. Everything works fine except that the first "if" condition does not evaluate as expected because it does not echo out the code that proves that it evaluated properly.I have a page(index.php) containing a form with post action from where the $_POST['pincode'] is coming from. So when if($pincode !== $_POST['pincode']) evaluates to true, instead of header location to echo the error message and come back to index.php page, what happens is that it routes to my checkpin.php (this script) and stays there.
NB: $_POST['pincode'] is a number input type in HTML.
$_SESSION['pincode']= $_POST['pincode'];
$conn = new mysqli("localhost","user","pass",'db');
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
$sql = $conn->query("SELECT pincodex, pinmatch FROM voters_reg WHERE pincodex = '{$_SESSION['pincode']}'");
$row_count = $sql->num_rows;
if ($row_count == 1)
{
while($row = $sql->fetch_assoc()){
$pinmatch = $row['pinmatch'];
$pincode = $row['pincodex'];
if($pincode !== $_POST['pincode']){
$_SESSION['error'] = "first error message";
header('Location: index.php');
exit();
} elseif ($pinmatch == $_POST['pincode']){
$_SESSION['error'] = "second error message";
header('Location: index.php');
exit();
} else {
$_SESSION['success'] = "success message";
header('Location: pinsuccess.php');
exit();
}
}
}
$conn->close();

Answer 1

Logically, $pincode should never be able to be not equal to $_POST['pincode']. Consider the following steps:
$_SESSION['pincode'] is set to $_POST['pincode'];
Rows are selected from your database WHERE pincodex = '{$_SESSION['pincode']}'
At this point, because of the WHERE clause, every row returned by your query will have pincodex == $_POST['pincode'].
You set $pincode = $row['pincodex'];
If there is a row, $row['pincodex'] will always equal $_POST['pincode'].
So, regardless of type checking, the condition if($pincode !== $_POST['pincode']){ can never evaluate to true, and your code will never enter that if block.
If a pincode is entered that is not found in your database, $sql->num_rows will return 0 and the code will not enter the if ($row_count == 1) block at all. I think this is most likely why your script is not redirecting as expected.

Answer 2

Try changing the if statement to if($pincode !== (int)$_POST['pincode']){