Simple PHP Login with .txt not working

This is login.php. A user enters a username and password on the previous page. Database stores information in the format "user|pass". Using the explode function to separate user and pass with "|".

$details[0] finds a match on the same line. But not for $details[1] even though the inputted data is correct with the actual .txt file.

$user = $_POST['user'];
$pass = $_POST['pass'];  

$db = file("database.txt");

$valid = false;
foreach ($db as $person) {
  $details = explode('|', $person);
  if ($details[0] == $user && $details[1] == $pass) {
      // Found a math to the database.
      $valid = true;
      break;
  }
}

Why is this the case?
Thanks