MySQL query runs without error but does not populate database - mysql

Question

Evening folks,
Having another of those "looked at this too long moments".
This code when run return the success message but nothing gets entered into the database table, no errors being thrown up, I know all the correct values are being received from _post but I can't see what's wrong, I have an almost identical query on another page and it works fine.
Can anyone see issues with the code?
if (isset($_POST['username']) && $_POST['username'] !== '')
{
$salted = md5($_POST['pass1'] . 'salt');
try
{
$sql = 'INSERT INTO users SET
username = :username,
firstname = :firstname,
lastname = :lastname,
email = :email,
password = $salted,
joined = CURDATE()';
$s = $PDO->prepare($sql);
$s -> bindValue(':username', $_POST['username']);
$s -> bindValue(':firstname', $_POST['firstname']);
$s -> bindValue(':lastname', $_POST['lastname']);
$s -> bindValue(':email', $_POST['email']);
$s -> execute();
}
catch (PDOException $e)
{
$error = 'Error adding submitted user.';
echo $error;
exit();
}
?> <div class="alert alert-success">User added to the database.</div> <?php
}

Answer 1

Summarizing comments here, for the sake of having an answer. Marked Community Wiki.
A string in your INSERT statement should be quoted.
password = '$salted',
You should use a parameter anyway.
password = :password,
. . .
$s -> bindValue(':password', $salted);
MD5 isn't the preferred hashing function for modern strong password storage. Neither is SHA1.
Try to use SHA256 or Bcrypt instead.
$salted = hash('sha256', $_POST['pass1'] . 'salt');
Salting is better if you use a random salt string per user.
Make sure your PDO instance is configured to throw exceptions.
$PDO->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
Always capture the PDO exception's error message, even if you don't output it to users.
error_log($e->getMessage());