Passwords not matching - php

Question

I'm switching over to PDO and trying to make my passwords in the MySQL database a little bit more secure, but unfortunately I've run into a little bit of a problem.
When a user registers, their password is treated as follows:
$pass = sha1($_POST['pass']);
And when a user logs in, the password they provide is treated exactly the same ($pass = sha1($_POST['pass'];)
The idea is then that I compare the two, and if they match, the user is logged in. The difficulty is, even if I enter the same password - "password", for instance - the encrypted password put into the database on registration does not match the encryption of the password when the user attempts to log in.
Does anyone know what the issue might be?
Full code:
$user = $_POST['user'];
$pass = sha1($_POST['pass']);
echo $pass; // This was just to check the two passwords
$db = new PDO('this is all correct');
$query = $db->prepare('SELECT pass, id FROM users WHERE user=:user');
$query->bindParam(':user',$user);
$query->execute();
$result = $query->fetch();
$storedpass = $result['pass'];
$storedid = $result['id'];
if($storedpass === $pass) {
header("Location: index.php");
}
else {
echo "Something went wrong";
}

Answer 1

sha1 should not be used to hash passwords. See the notice in the docs. You should use the new password_hash function instead, and the matching will be handled for you by password_verify.
Switching to the new hashing functions would likely solve your password validation issue while at the same time making your app much, much more secure.
If your version of PHP is less than 5.5, the new functions aren't available. A version for PHP 5.3.7+ is available on Github https://github.com/ircmaxell/password_compat.

Answer 2

You'd actually be much better off doing something like this:
$user = $_POST['user'];
$pass = sha1($_POST['pass']);
echo $pass; // This was just to check the two passwords
$db = new PDO('this is all correct');
$query= $db->prepare("SELECT id FROM users where user=:user AND pass=:pass");
$query->execute(array(':user' => $user, ':pass' => $pass));
if ($query->rowcount() == 1){
// authenticated
}else{
// not authenticated
}
Don't know if this will solve your problem though.